Will the Arab spring precipitate a sexual as well as a political revolution? It is an intriguing question, which the award-winning Cairo-based journalist Shereen El Feki explores in this account of a highly sensitive and still mainly hidden facet of the Arab world.

The book blends interviews, statistics, opinion polls, journalism and personal reminiscence. The author's grandmother pops up in most chapters, dispensing jaunty proverbial wisdom: "So long as it's away from my own ass, I don't mind," begins the chapter on homosexuality. Despite its breezy tone, the attempts to connect social and sexual developments are sometimes clunky: "These seismic shifts in Egyptian society are rocking Azza's marital bedroom, although the earth most certainly does not move when she and her husband make love."

If you are after a thoroughgoing scholarly treatment, look elsewhere. But Dr El Feki's position as a western-educated female Muslim, both insider and outsider (she grew up in Canada, the daughter of an Egyptian father and Welsh mother), gives the book an invaluable perspective and a different kind of authority.

Much of it makes for depressing reading. In most Arab countries, all sex outside marriage is prohibited. Some conservative clerics have even issued fatwas against married couples being naked during sex. In 2009, a Saudi Arabian who made the mistake of discussing his sex life on a satellite TV programme was sentenced to a thousand lashings and five years in jail for "publicly boasting of sin". That is the kind of mind-set the fundamentalist Christian governments of 17th-century Europe and north America would have applauded.

In practice, chastity is considered immeasurably more important for women than men, and marriage is neither private nor equal. The obsession with bridal virginity means that it remains de rigueur in Egyptian society to celebrate the husband's taking possession of his wife by publicly parading her bloodied bedsheets on the morning after the wedding. Many brides believe it's a husband's right to beat his wife if she refuses to have sex; the police tend to agree.

One of El Feki's spirited younger informants, a university-educated woman in her late 20s, is matter-of-fact about why she married in secret: "My parents, if they find out, they will kill me. Really. It happened in my family."

Even the Arab world's best-known sex therapist is implacably opposed to premarital sex. Her advice to wives: "He is exposed to many temptations outside the home. Be available to please him and do not give him a reason to make a choice between you and hellfire."

The consequences of all these taboos are unremittingly catalogued. The Egyptian police routinely inflict electric shocks, beatings and rape upon gay men. Around 80% of Egyptian girls have had their genitals mutilated, often their clitoris cut off: fear of female lust is a common justification. El Feki visits one of Cairo's hundreds of orphanages for unwanted illegitimate children. She explains the "prick-and-stick" approach to abortion, "in which the woman is knocked out with an injection and then hit about the back and abdomen until she starts to abort". She meets the pimps who arrange temporary "summer marriages" for male tourists looking to buy religiously compliant sex with underage girls. Along the way, she makes clear how far most Arab women share the sexist presumptions of their culture, even as they suffer its effects. Male sexual harassment and assault are "epidemic", yet most women take it for granted that "provocatively dressed" girls are asking for it. Most married women condone genital mutilation; 98% of Egyptians, male and female, disapprove of single mothers.

Yet El Feki tries to remain upbeat. To put things in perspective, she highlights national differences: the Gulf states are the most sexist; Tunisia's legacy of anti-Islamic dictatorship includes legalised abortion; Beirut is probably the least bad Arab city in which to be a lesbian or transsexual. Sometimes these snapshots are illuminating, though often they come across as padding for a book whose focus is on Egypt, and Cairo in particular.

Above all she seeks out the men and women on the ground who are trying to create a more equal and tolerant sexual culture, for unmarried couples, battered wives, prostitutes, and homosexuals.

What optimism the book conveys comes chiefly from the variety of feisty, outspoken women we meet. Female voices have been central to public life in the west ever since the Enlightenment: 300 years ago, their growing assertiveness helped bring about our first sexual revolution. Just as that breakthrough transformed western culture for ever, so too the rising consciousness of women across the Arab world nowadays is perhaps the most hopeful sign of slow but fundamental improvement.

When Barack Obama asked Shimon Peres what was preventing democracy in the Middle East, he replied: "The husbands." Sex and the Citadel hopes for the reverse: that political changes might bring about greater sexual liberty. Yet though it is clear-sighted about the recent rise of Islamic fundamentalism, it is wishful in presuming that until recently the Arab world was "open to the full spectrum of human sexuality". At different times this supposed golden age is located anywhere between the middle ages and the 1950s, yet all we get in the way of substantiation are references to classic works of erotic fiction (with their liberated "wives, concubines, slave girls, and prostitutes") and yet more family anecdotes: "My father, then a young boy, remembers being sent outdoors to play, returning to find the daya [a traditional midwife] throwing out an aborted foetus with the other remains of the day." Arab patriarchy, like our own, has deeper historical roots than this book suggests.

The other obvious, age-old restriction on sexual freedoms is religion. El Feki suggests that the problem is "not Islam but Muslims". She goes out of her way to stress the spread of clerical opinion on everything from masturbation, to "hymen repair", to anal sex within marriage.

Yet she sidesteps the more basic fact that as long as the words of the Qur'an and its prophet are treated as infallible, and their exegesis by male clerics remains the ultimate authority in sexual affairs, there can be no proper individual sexual freedom. That is not a problem of Islam alone, but of all fundamentalist interpretations of religion. Indeed, it mirrors what the western world was like for most of its history, until the Enlightenment – a society in which sex, like religion, was not private but public. The western past is doubtless an imperfect guide to the future of the Arab world. But it does suggest that freedom of conscience is a prerequisite for the creation of a distinct sphere of private life.

How far and how fast things will change is anybody's guess. Several of the book's activists are pessimistic. "Not now; maybe after two centuries," concludes one. Let's hope things move a little more quickly than that.

Faramerz Dabhoiwala is author of The Origins of Sex: A History of the First Sexual Revolution (Penguin)