I am African-American. We are a sentimental people in the main and we tend to track our own. We are aware of others of colour who cross our spaces. We look around asking: "How did she/he come to be here/there? Is his/her story extraordinary, coincidental or totally banal?"

At 80 years old, my dentist father has been a desegregator all of his adult life, both professionally and domestically. Although raised in Richmond, Virginia, he chose to rear his family up north, first in Boston, then in a Connecticut suburb of New York. When I call him to ask how things are going during the first week of the US Open, he tells me that the Williams sisters are doing fine, as is James Blake, and there are a young boy and girl playing in their first Open who won't get too far this time but are looking mighty good. Unsaid, I know the nature of the report he's going to give; unsaid, he knows what I want to hear: stories about black people coming on to traditional white fields of play and not just holding their own but kicking ass and taking names. Smiles, pride, a fist in the air.

So why the viscerally negative reaction, my gut literally roiling with distaste and disappointment, when I look at Condoleezza Rice, the first African-American female to be secretary of state of the world's one remaining superpower?

She is a powerful woman, often coming first in lists of the world's most powerful women. Unlike Hillary Clinton and Oprah Winfrey, she is seldom referred to by her first name only: as with Angela Merkel and Margaret Thatcher, she gets both her names. Her eyes, intelligent, usually veiled, often glittering hard, give up nothing. Her hair is now less iron-solid than it was but, as with Thatcher and Merkel, it is generally unmovable. And there is the posture: ramrod straight. The chin is held high even seemingly when notes are consulted, but that is very seldom, because Rice functions in public almost invariably without notes. A woman of impressive intellect - vast, profound and/or well-trained - holding her own, be it among or before the most powerful white men in the world. Again and again, she is generally the only non-secretarial black woman to be seen in such environments. Mercilessly kicking ass, taking names. Ready.

(A cultural footnote: back in the day, before any kind of mixing, before even Motown was heard on white radio stations, African-Americans had a play on the word "ready". If someone acted a fool, the jibe was: "He/she ain't ready." Not ready for responsibility or integration, ie interaction with white folks.)

So why am I so loth to look in her direction? She is not unattractive; our ages and backgrounds are reasonably similar. Yet I must force myself to look at her. She is family, attenuated family, deplored family maybe, but family none the less. I do not have to condone or even explain family misdeeds.

But I take her complicity in what I consider the most disastrous US administration in modern times very personally. I want to take her by the shoulders and shake, if not throttle her. But very much more, I want to know, why? Why the Republicans and these Republicans? Why the rigidity? Why the hubris? Why so little compassion for those less blessed than yourself? So intelligent, so capable ... how could you get it so wrong?

It is with these questions in mind that I came to Marcus Mabry's biography of Rice. A graduate of Stanford University during Rice's time there, like her a student of Soviet Russia, later a fellow of the Council on Foreign Relations, Mabry - formerly chief of correspondents at Newsweek magazine - is supremely equipped to examine his subject. He is also African-American and so gained access to family and friends who would have been far more circumspect with a white person.

Not unexpectedly I learn that Rice seemed to have popped "ready" from the womb. She was born in Birmingham, Alabama in November 1954, her parents coming from two families of strivers. Of modest financial means, but fierce pride, discipline and determination, her kin had made their mark and way in a city known for some of the most virulent racism in the old South. When John Rice Sr decided to abandon the cotton fields for book learning, he converted from Methodist to Presbyterian when he learned that the nearby Stillman Institute in Tuscaloosa, Alabama, offered scholarships for black men wanting to become ministers in that faith.

His son followed in his footsteps. On gaining his degree in 1949, Condoleezza's father, John Jr, moved to Birmingham, and met and married Angelena Ray, a teacher of music, science, maths and oratory at a local black high school. John Rice Jr was a huge bear of a man, gregarious and warm. The lighter-skinned Rays were proud and clannish, needing no one but their own.

An only child because her mother couldn't imagine dividing her love, Condoleezza was her family's perfect legacy. Reading music from the age of three, never fidgeting or dreamy, she was initially home-schooled and not allowed to play with the girl across the street unless her mother could watch her though open doors.

The US edition of Mabry's book is entitled Twice as Good. I expect that this was discarded for its lack of cultural resonance here in the UK, but among striving African-American families "twice as good" was the order of all days. We knew that good wasn't enough to achieve in the white world and many of us were reared with what Mabry calls the "affection of expectation". I myself did well in school. I knew this was expected of me, but I was also enjoying myself. However, when at 13 I learned that many of my (white) classmates were getting paid for their A grades, I ran this by my father. His response was: "You don't get paid to do your best. That's your job." I wasn't surprised (though I wouldn't have minded the extra quarters).

In Rice's upbringing things went far further. An accomplished classical pianist who spent hours practising every day, when she wished to play one of the Supremes in a school talent show, her father dismissed it as common. She would tap dance instead, and although Condoleezza had never tap danced before, she got by. She was being trained for solo stardom.

These were the years when the civil rights movement was at its height and particularly lethal in what was dubbed "Bombingham". In addition to the bombings, beatings, dogs, water hoses and mass arrests were all too frequent, but although John Rice was known for mentoring the youth of his community, neither he nor the Rays held with the collective mass protests led by Martin Luther King and his lieutenants. They were practical people, realists who believed in the power of diligently applied individual will to change one's situation and improve one's lot, and had no desire to be seen as part of a group - at least not this group.

Participants in marches were lower class, in their opinion and, most particularly, John Rice could not condone the morality of the city's famous children's crusade, when hundreds upon hundreds of black children left school and were jailed for marching against civic directive. He would not allow his daughter to participate, but he drove her downtown to observe from the safety of their car. He perched her on his shoulders outside a fenced outdoor detainment camp. These are images to be reckoned with, the treasured special child insulated from harm within the considerable steel of a 1960s American automobile and observing world-challenging turmoil from the eyrie of her father's high and ample shoulders.

Via her father's hard work, the Rice family's prospects improved, and in 1968 they moved to Denver, Colorado, where John's graduate studies at the University of Denver resulted in an administrative appointment at that school. For the first time the family were living, working and going to school in a white environment.

After a period of readjustment, Rice continued her familiar pattern of academic excellence combined with the solitary disciplines of piano and now figure skating training as well. Then, in the summer after her second year at Denver, came her first crisis of confidence, when she attended the music school of the Aspen Music Festival. Up to that point, Rice had been dedicating countless hours of practice toward her career goal of becoming a classical pianist, but at Aspen she encountered students far younger than she who could read by sight things that had taken her an entire year to master. Not wanting to be mediocre, she decided to change course.

Her teacher was not surprised. He had recognised early on that although Rice was technically competent, she was too emotionally detached to be a great musician. Rice's later reaction to queries about losing the dream of her early years were words that had by then become her mantra: "I don't do life crises. I really don't. Life's too short. Get over it. Move on to the next thing."

That next thing was disciplined study of the Soviet Union, first at Denver University, then at Notre Dame University for a masters degree, then back to Denver for a brief interlude, and finally on to Stanford with a predoctoral fellowship. She charmed all whom she encountered. She was competent, tireless and a pleasure to be around. She was also an African-American woman shining in an unexpected field, something that worked very much to her advantage during a time of affirmative action.

A pause to consider what Rice's years of higher education were and what they were not. Nothing in her educational progress seemed to diminish her family-inculcated feeling of distinction, but why was there no impulse to push the educational envelope by attending more competitive schools? Yes, she was young when she entered Denver, with all the sheltering, probably younger than her years, and after the loss of her musical dreams and the finding of a political science mentor at Denver University (Madeleine Albright's father), one can understand why she chose to complete her undergraduate studies at home. But with all this academic self-confidence, why was there no desire for graduate study in the Ivy League or Berkeley or the University of Chicago, to hone her intellectual skills via challenge from those at least her equal? Her father was a university administrator concerned with affirmative action. She would have known that elite institutions were welcoming qualified African-American students. Did she eschew the possibility of being just another smart black girl whose gifts might not stand out so magnificently with other smart black girls about, black girls from equally, far more and far less supportive environments - the academic equivalent of Aspen, in fact?

Rice's university years were a time of tumult on elite American campuses, anti-Vietnam war and pro-Black Nationalist strikes, teach-ins and demonstrations. It was chaotic, time-consuming and, yes, I can attest, time-wasting to some degree. For one programmed for ordered perfection, such an environment might have been repellent; but in the unruly hair and dogmas, the disorderly passions, was a provocative creativity as students probed the meaning of being American and human in changing times. From her eyries in Denver and South Bend, Indiana, where the greatest passion was for football and most black students were on sports scholarships just trying to hold their own, Rice was above that messy fray, undistracted, not having to justify her decision not to be part of any group to folk who would have kept on asking, not having to defend her ideas before those of a similar background who had the abilities to question her worth. She was thus able to reinforce her steely belief that nobody was her intellectual equal, certainly no person of colour in her peer group.

Time and again in interviews, Rice maintains that despite the manifold physical threats to black people in Birmingham - and even the death of one of her school friends in the infamous church bombing of 1963 - it was not rabid racists who struck the most fear into her heart (at age eight) but the Cuban missile crisis the year before. In 1968, when she was 13, it was not the assassination of Martin Luther King that tore at her soul but the Soviet suppression of the Prague Spring. Nothing Mabry or any other questioner has suggested has ever induced her to sway from this stance.

True to his journalistic calling, Mabry does not editorialise inordinately on this point, but he is far younger than Rice (and me). I am sure he has done his homework, and he is bound to have heard many tales of those horrible weeks in 68 during the course of his young life, but not having been around then he cannot know in his gut how the death of Dr King had such a visceral impact on Americans, both black and white, who weren't spawn of the devil. To claim more concern for an unknown foreign people thousands of miles away when, regardless of your family's political notions, you have heard this man's eloquence in defence of your freedom and personhood, when all around you people are heaving with grief, anger and despair, bespeaks a dishonesty of colossal dimensions.

Rice was not alone in her desire to stand out from the rank and file of a debased minority. Many of us did this. We studied Chinese, Arabic, European painting, Indonesian architecture, Hindu cosmogony and mushrooms. We were well aware of our exceptionalism - you couldn't not be with white professors and students wondering what you were doing in unusual places, often to our faces - and eager to push wide the bounds of what people thought we could do. But by and large we felt it unnecessary to go to Rice's lengths to shore up our exception. Or maybe she is being truthful and thus displaying a lack of human empathy that is even more disturbing, indeed smacks of the sociopathic.

Rice's appointment to Stanford in 1981 (as an assistant professor in political science) was affirmative action in the best sense. She was not, on paper, the most qualified for the appointment - her colour and gender had tipped the scales in her favour - but once in situ she ran so fast, far and well that she left her peers in the dust. She was a dynamic and well-liked teacher, an ever-prepared and charismatic speaker. In 1984, she was noticed at a conference on the future of the cold war by Brent Scowcroft, the former general who was soon to be National Security Council advisor to President George Bush Sr. In 1989, he brought her to Washington as the National Security Council director of Soviet and east-European affairs in Bush Sr's administration. In so doing, Rice became an integral player in the reunification of Germany and the denouement of the Soviet empire, distinguishing herself on the international stage.

Though Stanford's campus felt small upon her return in 1991, her professional life continued as one success after another. She wanted corporate experience and, via her Republican contacts, was appointed to the executive boards of Chevron, Hewlett Packard, Transamerica and the International Advisory Council of JP Morgan. She became a paid consultant for ABC News on Soviet affairs, and in 1992 was appointed provost of Stanford University, the youngest in its history and, of course, the first to be African-American.

In 1952, when Alabama's Democratic party was not allowing black voter registration, its Republican party had welcomed John Rice into its fold, and he had always told his daughter to think Republican. Each Republican was an individual, not part of a group, while in 1980 the Democratic presidential nominee Walter Mondale was still characterising black people as hapless victims, at least in Rice's eyes. Infuriated and repelled, she voted for Ronald Reagan, attracted by his strength, and saying: "I'd rather be ignored than patronised."

While she never seemed an ideological Republican prior to her time with Bush Sr, upon her return to Stanford, many of her friends - who, interestingly, are in the main far more leftwing than she is - detected a hardening in her approach to issues such the affirmative action that had greatly assisted her own rise. She was also extremely autocratic. She was intelligent; she was always right. She believed deeply that she was God's instrument, guided by His will. Despite her inexperience as a manager, she felt that compromise and coalition-building were an unnecessary waste of time. She could be ruthless. She accomplished much, was also feared - and, of course, she was exceptional.

There had never been much room in Rice's life for relationships, but she was something of a flirt in her first years away from home. She was partial to football players and most attracted to the bad boys among them. This is not so surprising. For someone loth to share the inner workings of her heart and mind, bad boys are ideal. Bad boys titillate, make you feel daring by following their leads, but with their tendency towards narcissism they aren't going to probe very deep beyond what they see. They are not worrying about the truth in themselves so they are not going to search for the truth in you.

In 1998, accepting an invitation from Bush to come to Kennebunkport, Maine, to meet his son George W, Rice encountered the quintessential bad boy, with a near-direct avenue to the heart of American power. They clicked. They more than clicked. They both considered themselves outsiders. He admired her brains, she his leadership instincts and "compassion-ate conservatism". They shared a sense of humour and a love of sports. And the rest is our current history.

Originally drafted in to school the second George in foreign policy and to manage the coterie of advisors dubbed the Vulcans, Rice and her exemplary exceptionalism became a key weapon in the overall campaign. Crowds loved her, her charm, her charisma, her life's example of the power of individual will. When the election in 2000 was finessed in his favour, it was only natural that Bush would want Condi by his side. During the first term she was National Security advisor; in the second she is the secretary of state.

As with his subject's earlier life, Mabry details the progress of Rice's involvement with Bush Jr with cogent application - her varying levels of success in outmanoeuvring the administration's behemoths of malice, Donald Rumsfeld and Dick Cheney; her continuing and steadfast belief in God and in herself and in the man to whom, say family and friends, she can't say no; the continuing and steadfast refusal even now, after four years of Iraqi debacle, to concede misguided decisions, let alone failure.

The question that can be asked is this: is this continuing and steadfast refusal to go off script because she won't, or because she is not able? Having always been insulated from the chaotic mix of the world by her family and then through her own choices, having never cultivated the virtues of spontaneity and creative thinking beyond the goals of careerism, Rice formulated her ideas of power through a very narrow prism. She is not alone in this. Regrettably, few foreign policy advisors in many governments have taken the time to learn the workings of hearts and minds operating on bases other than their own. Unfortunately for Rice, her time at the helm has coincided with the splintering of political theories of what works and what does not. Because of this, she was ill-equipped to guide her feckless leader through so shape- shifting a time.

In reaching so high, her exceptionalism could no longer be judged by the mere fact that she had reached such a pinnacle, but by how she performed when she got there. The working consensus at this point in 2007 is that she is working more efficiently at the State Department than at the National Security Council, no longer in such physical and symbiotic closeness to her employer, but that these will be looked upon as embarrassingly tainted years and in this she will have been an integral factor.

One could ask, why the moral outrage? Rice has become a politician and this is said to be the way politicians behave. But that would be forgetting the holy shroud of morality that drapes about the shoulders of American society. We are meant to be a nation conceived in liberty via the blessings of God. Is not one of the first tenets of America's God, and Rice's Christian belief, to protect the common welfare and give succour to the less fortunate?

I may be sentimental, but African-American sentimentality is but American sentimentality. Creating and trading on her exceptionalism, Rice has gone far further than most of us. Is this proof of her superiority, her willingness to adapt, or both? Despite her disassociation from the life and messages of Martin Luther King, she is the epitome of his wish for his children that they be judged "not by the colour of their skin but by the content of their character". In this, most certainly, if not in all that she might have imagined, Condoleezza Rice has succeeded.

· Candace Allen's first novel, Valaida, was published by Virago in 2004. She studied at Harvard University and was the first African-American female member of the Directors Guild of America.

· This article was amended on Tuesday December 11 2007.