For Tom Wolfe, the New Journalism was defined by the appearance of all kinds of literary devices in non-fiction writing, but chiefly by an unwillingness to adopt the traditional journalistic tone of polite neutrality. He made the business of voice appear as if it was simply a matter of style, a confident new generation trying on a linguistic version of one of his own well-cut suits. While this surface stylishness characterises Wolfe’s own voice, with its caustic social observations and bravura displays of writerly technique, for other writers the chance to speak in an unmediated first person fulfilled a more urgent necessity. It allowed Michael Herr, on assignment in Vietnam for Esquire and Rolling Stone, to write about his own terror and confusion as he drifted through the war zone, and it allowed Joan Didion, in The White Album, to weave details of her anxious upscale-Californian life into a startling account of the collapse of Sixties idealism.

No one took the voice of the journalist further away from ‘neutral background’ (or seemed less able to stop himself doing it) than Hunter S. Thompson. Even at the start of his career, he was no believer in journalistic neutrality. Born in Louisville, Kentucky in 1937, Thompson was often in trouble with the police, spending his high-school graduation day in Louisville jail as part of a six-week sentence for robbery. A contribution to his school magazine railed against ‘security’, eulogising, in tones apparently inspired by Marlon Brando in The Wild One, the ideal of ‘true courage: the kind which enables men to face the unknown regardless of the consequences’. That outlaw pose adopted in his teenage conflicts with Southern authority has never been dropped. In ‘The Kentucky Derby is Decadent and Depraved’, an influential essay written in 1970, he described a day at the races – the centrepiece of white Kentucky’s social calendar – which he spent gleefully spreading the rumour of a Black Panther-inspired riot.

After school he joined the Air Force, and edited the sports, section of his base newspaper. He complained to a girlfriend of the ‘blood-curdling routine’ and promised that ‘just as soon as I sell a novel or two, I will buy a plot of land and ... fence the whole thing off and operate a small-scale nudist colony where I can have nightly orgies and not be bothered by the world and its idiots.’ The US Air Force was determined not to let him have it all his own way. A 1957 personnel report noted that ‘in spite of frequent counselling’ the young airman-journalist ‘leans so strongly to critical editorialising that it was necessary to require that all his writing be thoroughly edited before release’.

After the Air Force, Thompson travelled around America, sometimes writing for newspapers, often broke, always obsessively working on The Rum Diary, the novel he hoped would make his name. Ironically his fictional ambitions were gradually absorbed into the journalism and The Rum Diary has remained unpublished until now, almost forty years after its composition. A hard-bitten story of love, journalism and heavy drinking, it never strays too far from Thompson’s own life. The pull of the real was already exerting itself On the 22-year-old writer.

Though he was filing reasonably conventional copy for his various employers, his tendency to attract trouble, usually involving some combination of trouble’s classic elements – drugs, alcohol, cars, guns and women – meant that his presence often sparked off events far more interesting than those he was supposed to be covering. Later in his career the ‘story’ as independent entity was to disappear almost entirely from his work, which became a fractured series of tales about Hunter (mad, bad and dangerous) and his behaviour (inspired, erratic, paranoid). His ability to articulate the undercurrent of ‘fear and loathing’ running through America ultimately led to his adoption as a kind of soothsaying holy fool for the counter-culture.

In the late Fifties and early Sixties Thompson travelled round the US, lived at various times in a cabin in the Catskill Mountains and a beach hut in San Juan, Puerto Rico. He also spent rime in New York, sucking in the post-Beat atmosphere, while irritating his neighbours with week-long parties (‘a sort of human cesspool with ever-changing ingredients’) and drinking binges. In 1960 he moved to the idyllic wilds of Big Sur, on the Californian coast. ‘Reading the New York Times in Big Sur can be a traumatic experience,’ he wrote. ‘After living here for a few months you find it increasingly difficult to take that mass of threatening, complicated information very seriously.’ Though Big Sur was used to accommodating the habits of creative artists, Thompson alienated the community with his wildness and blunt manners, and eventually made himself persona non grata by publishing a controversial exposé of ‘a Pandora’s Box of human oddities, and a popular sinkhole of idle decadence’.

Leaving Big Sur under a cloud, Thompson spent 1962 in South America, filing political stories for a variety of newspapers. Thompson’s friends heard about a different side of the trip, in letters which contained gothic descriptions of his hand-to-mouth existence. To Paul Semonin, probably his closest friend, he wrote of an eight-day river journey through Colombia:

The crew is primitive and vicious-looking and the captain is an old river toad who can’t understand why I’m here and doesn’t much care for it. His daughter is here too, but she is scraggy. I was dealing in a whorehouse last night but refused to pay and could not make my concepts understood. I convinced the lovely but the chickenheaded madam held firm. Fuck them all. These Latins are all whores in their own various ways – even the presidents.

He returned from a continent of dirty hotel rooms and beetles ‘the size of god’s ass’ to find that his work was becoming well-known. Then, in 1966, he became internationally famous for his book-length portrait of Californian motorcycle gangs, Hell’s Angels. Rather than write a scare story from the safety of his newspaper office, Thompson bought a bike and rode with the outlaws, hearing their stories first hand. Eventually he was ‘stomped’ for his trouble, but at the price of a few broken bones gained the trust of the Angels, introducing them to Ken Kesey’s Merry Pranksters, who invited them to Kesey’s La Honda ranch for a party that has since, in accounts by Tom Wolfe, Allen Ginsberg and others, achieved mythic status. La Honda, with its gang of fancy-dress hippies, was ‘one of the strangest scenes in all Christendom – a wild clanging on tin instruments on a redwood hillside, loons playing flutes in the darkness, mikes and speakers planted all over, mad flashing films on a giant trampoline screen’ Thompson thought Kesey was wasting his talent: ‘in all it was pretty depressing – that a man with such a high white sound should be so hung up in this campy kind of showbiz.’

Thompson’s work reached a kind of frenzied peak in the early Seventies with his repeated savagings of Richard Nixon, whose ‘very existence is a monument to all the rancid genes and broken chromosomes that corrupt the possibilities of the American dream’. For all such dizzy heights of vitriol, his masterpiece is undoubtedly the hallucinogen-fuelled attempt to cover a desert road race which became Fear and Loathing in Las Vegas (Terry Gilliam’s film of the book, which features an unlikely Johnny Depp as Thompson, has its UK premiere in November). In this warped successor to Kerouac’s On the Road, the journalist and his ‘two hundred pound Samoan attorney’ fill a convertible with an assortment of narcotics and drive deep into the America of casinos, convention hotels and car hire depots, all the time existing in a dangerously altered state. The assignment turns into a dissection of the paranoia underlying the banalities of the service sector, and a revelation of something rotten in the state of America. In the book’s most famous scene, Thompson attempts to check into a hotel while fighting the creeping ‘realisation’ that everyone else in the lobby is a giant lizard.

Material which in other hands would be solipsistic and self-serving – there is, after all, nothing as boring as other people’s drug stories – has always been anchored by Thompson’s journalistic skill. His gift for reporting, his humour and political sense have made his ‘gonzo’ version of the New Journalism the most widely imitated style in Nineties feature-writing. Sadly, the self-confidence Tom Wolfe identified thirty years ago has largely degenerated into self-abuse, as myriad wannabe gonzos recount the minutiae of their dining and travel arrangements. Thompson, meanwhile, has become a national treasure, ensconsed in his Aspen ranch, toking joints, shooting guns, receiving visits from tremulous profilers, and occasionally emerging to traumatise bureaucrats, bigots, politicians, pen-pushers, yes-men and anyone else who could be reasonably accused of following the herd. He is already, at 60, the subject of several published biographies, all of which he hates.

A book of letters is a blast against the biographers, but for a writer who has made a stylised, steroid-enhanced first person the centre of his work, its publication is not without risks. The world has had almost forty years of the supposedly unmediated textual ‘I’ of Hunter S. Thompson, in every conceivable mode and mood from forth-right harangue to gibbering in the corner. So is the ‘I’ of the letters merely more of the same? Or is the epistolary Thompson different from that of the essays, articles, prefaces and interviews? Will it reveal that while everyone believed in the freak-show version, Hunter was just hamming all along?

As it turns out, The Proud Highway is something of a triumph, as an account, not just of the social and political upheavals of its time, but of the strange progress of Thompson’s self-construction. In nearly seven hundred pages of text, the book covers just 13 years of letter-writing (1955-67). The editor estimates that Thompson has written twenty thousand letters in his lifetime, which is almost one a day since birth, if you give him credit for starting early. It is only Volume One of The Fear and Loathing Letters, and stops just as the author is finding his stride, getting famous by writing Hell’s Angels. The best stuff, written out of the dark, hallucinated, polyester-clad sodom of the early Seventies, is surely yet to come.

A first clue to the high weirdness which unravels in The Proud Highway can be found in a letter written but not sent to one of his many girlfriends by the 21-year-old Hunter, newly-fired from a local newspaper job for kicking a vending machine. In the middle of a long romantic ramble he reflects: ‘The Hunterfigure has come to another fork in the road and the question once again is “where do we go from here?” ’ This is more than just rhetoric. The appearance of the ‘Hunterfigure’ presages doom for any reader foolish enough to stash these letters in a box marked ‘Life’ next to another marked ‘Work’. The Hunterfigure – Frankenstein’s monster in a Hawaiian shirt with a bellyful of tequila – was to colonise the first person singular entirely in his published writing.

The fascination of The Proud Highway lies in watching the spawning of the Hunterfigure, drip-fed on booze, insomnia, target practice and hatred of authority. Perhaps it’s no stranger than watching any other writer find a voice, but it is compelling that it should be letters – personal communications with lovers, friends and relatives – that serve as the petri dish for cultivating this most public of personae. Sooner or later the gnawing suspicion creeps up that the old Hunter S. Thompson no longer exists. He has been done away with, buried under the floorboards at Owl Farm, and the Hunterfigure, all nervous energy and itchy trigger finger, has taken over. This is a disturbing conclusion, given his tendency to make comments like this:

I would give a ball to wake up tomorrow on some empty ridge with a herd of beatniks grazing in the clearing about 200 yards below the house. And then to squat with the big boomer and feel it on my shoulder with the smell of grease and powder and, later, a little blood. I have come to the point where I think I could kill humans as easily as deer or wild Pigs.

This scary, macho, unhinged man becomes hilarious when you discover that this is literary criticism, a response to a ‘stupid shitty book by Kerouac called “Big Sur” ’.

Judging the degree of leg-pull in any Thompson letter is far from easy. One minute frothing and dangerous, in the next breath he will write swoonily to a girlfriend: ‘you’re ... still the same Ann Frick I remember from what now seems a million hazy dreams ago.’ Just when you are comfortable with the oscillation between Byronic hellraiser and lovelorn ‘Hunty’, you stumble on Thompson’s letter to his mother. Strapped for cash in San Juan, Puerto Rico, where he has schmoozed his way into a job as a sports reporter, he confides: ‘the main problem here is clothes. Everything is frightfully expensive and no one on the island can tell me where to get a cord suit ... Would it be possible for you to buy one there and send it to me? Make it my birthday present.’

Early on these characters seem weirdly separate, but through the course of the years of The Proud Highway they are all assimilated by the Hunterfigure, who bolts them together and deploys the resulting personality as a satirical weapon of mass destruction. Son, lover and lone gunman are not his only components, however. In his twenties, Thompson experiments with textual moods based on the styles of writers like Mencken, Hemingway, Fitzgerald, Kerouac and Dos Passos. He makes intense studies of these men, typing out long passages of their work to get a feel for their rhythm; the substance of the letters he writes between bouts of typing depends as much on who he’s reading as what he’s feeling.

Thompson also writes in a mode which approaches straightforward ‘character’. Enter the millennial nutcase who answers threatening letters from debt collectors with religious rantings (‘This atomic fallout is God’s WRATH! With the end of the world right on top of us, I can’t afford to work’) and the dope dealer who has misunderstood an article in the Village Voice (‘Say man, I’m bein’ bugged by the police and your damn paper’s the cause of it all’). After a while you just have to stop trying to distinguish the voices and sit back to enjoy the trip.

The Proud Highway shows Thompson in mortal verbal combat with editors, neighbours, landlords and vendors of faulty goods. Grievances are listed, failings are itemised, the guilty are held to account: ‘Gentlemen: I cannot tolerate the horrifying color combination of the checks and check holder you sent me’; ‘Sir: I would appreciate knowing if you mean to continue the stupid, vicious “Zip Code” system.’ These spats (whose occasions range from magazine rejections to the Book of the Month Club’s attempt to collect a debt) have an incongruous personal quality. Thompson persists in treating the bank, the State Department, the Postmaster General’s Office, as if they were individuals, susceptible to humour, flattery, wheedling or plain browbeating.

His seemingly perverse insistence on face-to-face confrontation occasionally exposes cant and hypocrisy. In 1964 he offers his services to President Johnson as governor of Samoa (‘My position at this time is in flux enough to allow my serious consideration of such a move’), then withdraws the offer in protest at the escalation of the war in Vietnam. Scolding LBJ (‘start acting like a thinking human instead of a senile political beast’), Thompson, at this point an obscure hack, places himself on the next metaphorical barstool to the President, insisting on his right to address the Administration as an equal. Lack of emotional engagement seems, throughout The Proud Highway, to be the crime which Thompson abhors. Again and again he insists that things happen because people, particular individual people, make them happen. And if you don’t like what people do, you should confront them. Applied to the smoke and mirrors world of US politics, it taps into old-fashioned American ideas about individual liberty and plain talking.

The true voice of Thompson is revealed to be that of American moralist. Certainly he is a misshapen sort of moralist, one who often makes himself ugly to expose the ugliness he sees around him. And sometimes he’s just ugly for the sake of it – this is why he sometimes comes over as an out and out asshole, whining about money, boring people about his unpublished novel, making a drunken fool of himself and generally using the facilities and not cleaning up afterwards. His prodigious intake of drugs and alcohol, coupled with his love of guns, speed and what one high-school teacher referred to as his ‘show-off Marlon Brando swagger’, has led to him being canonised by hedonists around the globe, who have made him a poster-boy for the ‘party until they drop the bomb’ tendency. For the same reasons he is largely dismissed by those who require their writers to behave like grownups. This is a shame, since Thompson’s capacity for mayhem is just a minor side-effect of a personality that functions as a machine for exposing liars and hypocrites. A few missed nights’ sleep and the occasional broken window seem a small price to pay.