There's a memorable passage in Tom Wolfe's hyperactive self-advertisement of 1973, The New Journalism, where he describes 60s New York as "a hulking carnival pandemonium with a big grin on". Wolfe's competitive writer's fear was that "some enterprising novelist was going to come along and do this whole wondrous scene with one gigantic daring bold stroke. It was so ready, so ripe  beckoning... but it never happened." Instead, the man in the white suit stepped into the breach himself to create "the non-fiction novel". Wolfe and the New Journalists plugged American prose into the mains, giving it an intravenous shot of a dangerously addictive treatment.

Ben Fountain is a former Texas lawyer who caused a mild sensation in 2006 with a collection of stories, Brief Encounters with Che Guevara: great reviews, comparisons with Graham Greene and John le Carré, and the accolade of a Malcolm Gladwell study of "late bloomers" in the New Yorker. He's now in his mid-50s and this is his first published novel.

So what's it about? The short answer is Iraq. Billy Lynn is a member of Bravo Company, one of eight US servicemen who emerge unscathed from a firefight to be brought home by the Bush administration for a victory lap. The climax of this promotional tour, and the meat of this novel, is their appearance at the Dallas Cowboys stadium as part of the halftime show on a Thanksgiving afternoon. By bringing the war back home, Fountain has come up with a clever and imaginative take on the classic American combat novel. He's done it with the kind of ambition that sent shivers down the spine of the young Tom Wolfe. Fountain is a child of the Wolfe generation.

Age and achievement are as likely to go well together as to be at odds. Daniel Defoe wrote his first novel, Robinson Crusoe, at 58. But Ben Fountain's age only becomes an issue because  beyond question  he has drunk deeply at the heady well of Wolfean Kool-Aid. Here, for instance, is Billy at home with his family in "the three-bedroom, two-bath brick ranch house on Cisco Street with sturdy access ramps front and back for his father's wheelchair, a dark burgundy motorised job with fat whitewalls and an American flag decal stuck to the back." Whoah! as Wolfe might say.

As telling as Fountain's over-revved, high-octane style, with its "nina leven" and "DeeeterrRRRminaaaAAAtion", is the "non-fiction novel" point-of-view. Is this Billy Lynn's interior monologue, or Fountain's? Where does one cease and the other begin ? This is not a novel told from the inside out but a made-for-TV war story narrated from the outside in. Fountain describes Billy's recollection of the company's famous firefight: "All your soldier life you dream of such a moment and every Joe with a weapon got a piece of it, a perfect storm of massing fire and how those beebs blew apart, sights not to be believed and never forgotten..." The unintended consequence of Fountain's bravura performance is to reduce the experience to words and style. It is, as advertised, extraordinary writing, but essentially fiction for non-fiction readers.

Ben Fountain's blinder of a first novel has been a long time coming. Fountain is such an egregious late bloomer that, a few years ago, Malcolm Gladwell wrote a New Yorker article about him. Back in 1988 he left his job as a property lawyer in Dallas, Texas, to write at his kitchen table; his first book, the acclaimed short story collection Brief Encounters with Che Guevara, was not published until 18 years later, in 2006. Now, with Fountain well into his 50s, his full-length debut has finally emerged  a fierce, exhilarating novel about the Iraq war.
Billy Lynn's Long Halftime Walk features no more than a few glimpses of battle. It's set on the home front, in 2004 or thereabouts, over one long Thanksgiving Day match at the Dallas Cowboys' stadium. As Karl Marlantes, the Vietnam veteran and novelist who dubbed it "the Catch-22 of the Iraq war", explained, it is a book about "the American way of watching war". And it is terrific: eloquent and angry, funny and poignant. It doesn't particularly resemble Catch-22, but it recalls all sorts of good things: the delirious Playboy bunnies stadium scene in Apocalypse Now; the outrageous military banter in Kubrick's Full Metal Jacket; the all-American cacophony of Tom Wolfe when he was still funny; Norman Mailer's anatomies of US celebrity; perhaps even the baseball game at the start of Don DeLillo's Underworld.
Bravo squad are heroes. They've been involved in a firefight in Iraq, in which they not only tore apart a group of insurgents  "beebs" or "hajjis" in the army's harsh dialect  but were filmed doing so by an embedded journalist. As a reward they have been plastered with medals and sent home on a two-week propaganda tour. The novel is set on the last day, just before they fly back to Iraq. The men of Bravo are "feeling soft, sated, bleary, under-rested and overproduced" after days of press conferences and nights of bars and strippers. For the eight soldiers, the trip is an ambiguous experience, to say the least, since they also lost one of their men during the fight. "It's kind of weird," says Billy, the book's 19-year-old protagonist. "Being honoured for the worst day of your life."
Most of all, it's hard work dealing with the American public, being "passed around like everyone's favourite bong" from the people in the hotel lobbies and football stands to the Texas super-rich in their corporate boxes. Faced with a bona fide war hero, they "go a little bit out of their heads. They do! They mash in close, push and shove, grab at his arms and talk too loud" The book opens with "tag teams of grateful citizens" trampolining "right down the middle" of Billy's hangover, and their patriotic words tumbling around his brain: "terrRist"; "freedom"; "nina leven"; "currj"; "sacrifice". Having fought for these people, he looks at them anew, and finds them suddenly troubling: "There's something harsh in his fellow Americans, avid, ecstatic, a burning that comes of the deepest need. That's his sense of it, they all need something from him, this pack of half-rich lawyers, dentists, soccer moms, and corporate VPs, they're all gnashing for a piece of a barely grown grunt making $14,800 a year."
Meanwhile, a movie producer is trying to sell their story to Hollywood. This is the book's theme: everyone wants a piece of the Bravos. But how much are they willing to pay?
There's one long flashback in Billy Lynn, describing Billy's return home to a small Texas town, and some brief passages set in Iraq. Otherwise, it's a day-long set piece evoking America "as a nightmare of superabundance". The Bravos eat a disgustingly big lunch; meet the Dallas Cowboys, "industrial-sized humans" with "beer-keg heads and redwood necks"; listen to grotesque speeches from Norm Oglesby, the team's unlovely owner. At the centre of the book, there's the half-time show, fronted by Destiny's Child: a jingoistic circus in which the Bravos are forced to march next to cheerleaders and scantily-clad dancers  "porn-lite, out of its mind on martial dope".
The novel is niftily postmodern, in that it deals with a heavily mediated reality. Bravo squad aren't even called Bravo squad, but that was what the "Fox embed" christened them. They hear their story being spun in real time: "Carl, what can I say?" says Albert, the movie producer, on the phone. "It's a war picture  not everybody gets out alive." The stadium is dominated by the huge "Jumbotron" screen; Billy wonders whether "maybe the game is just an ad for the ads". But Fountain, like better-known writers of his generation such as Jonathan Franzen and David Foster Wallace, has dragged this ironic, media-saturated style back in the direction of sincerity, with rich, sharply drawn characters that you care about. Beneath the dazzle, there's a story as old and simple as Kipling's poem "Tommy": "They sent me to the gallery or round the music-'alls, / But when it comes to fightin', Lord! they'll shove me in the stalls!"
Billy Lynn isn't perfect. The plot strands holding the set pieces together are thin: Billy's flirtation with a cheerleader is, as the book itself acknowledges, "the sort of delusion a desperate soldier would dream up". And the novel is sometimes coarsened by its political agenda. "In case you haven't noticed this is a highly partisan country we live in," says Billy's sergeant; and George W Bush and Dick Cheney get an entertaining kicking. People who support the war, such as Billy's horrendously bigoted dad, tend to be inferior human beings; Bravo squad are suspiciously liberal. Mostly, Fountain does an excellent job of grafting an alienated, educated, leftish perspective on to his cast of young soldiers, but at times the mask slips. "They love to talk up God and country but it's the devil they propose, all those busy little biochemical devils of sex and death and war that simmer at the base of the skull," thinks Billy  a great line that doesn't sound much like a 19-year-old who barely graduated from high school.
But then if the novel had a quieter, more realistic voice, it wouldn't be half as fun or interesting. Fountain has a marvellous ear for dialogue, and Billy Lynn is written in a sharp, profane language that makes English English sound terminally dull. Even the rain is rude: "It's raining, sort of, the air pilled with a dangling, brokedick mizzle." Scores of smart metaphors and similes zip by; "their faces set with the pinched look of angry vegans"; "forcing the cheer like Christmas lights in the poor part of town". Billy Lynn is an exhilarating read, and convincingly  if belatedly  damning of Bush's America.