Michael Herr wrote the great Vietnam book, one of its best films - Full Metal Jacket - and had a nervous breakdown in between. Now he's written about his friend Stanley Kubrick and he's not interested in the war. Or so he says...

Sitting on a garden bench - the sun, dappled by trees, streaming onto the lawn - it all seems impossibly far away. It is impossibly far away.

The corpse was the worst thing we'd ever seen, utterly blackened by now, the skin on the face drawn back tightly like stretched leather, so that all his teeth showed.

A light, warm breeze blows into his face and Michael Herr, master of war journalism, pulls down the peak of his baseball cap. It's not just that those who line up to praise his book, Dispatches , above all others include John le Carré, William Burroughs and Tom Wolfe, it is that he invented a genre, a new way of writing about war, the cruelty of war, the pity of war and the savage, hollow laugh of the warrior.

It was at this point that I began to recognise every casualty, remember conversations we'd had days or even hours earlier, and that's when I left, riding a medevac with a lieutenant who was covered with blood-soaked bandages. He'd been hit in both legs, both arms the chest and head, his ears and eyes were full of caked blood, and he asked a photographer in the chopper to take a picture of him like this to send to his wife.

Now, Herr says, he has 'cleaned it all out. People keep asking me to go and write about war for them. I say: "Haven't you read my fucking book? What the fuck would I want to go and do that for?" Publishers keep sending me books about Vietnam; I wish they'd stop. I'm not interested in Vietnam. It has passed clean through me'.

Instead, Herr has just produced a book about one of the most remarkable encounters to come out of his time in Vietnam - his friendship with Stanley Kubrick. It thereby blends the two boldest influences in Herr's living past (family apart). The third and present influence, and the most intriguing, is 'the reason why I did clean out and why I'm not crazy any more' - that will unfold later on during the conversation on the garden bench, with Herr swirling a mug of coffee round and round, and smoking half a cigarette at a time.

Kubrick is Herr's first volume since his strange and brilliant book about the life and death of the radio broadcaster Walter Winchell. Kubrick is a captivating little book rather like an Arthur Miller play: it plays out on a small scale, but invokes the epic themes of friendship, art, sex and war. It is intimate, honest and affectionate to the point of being able to say: 'I don't want to give the impression that I didn't get extremely irritated, that I never thought he was a cheap prick that his demands and requirements weren't just TOO MUCH.'

And there's this gratifying insight: 'They say [Kubrick] had no personal life,' writes Herr of his friend, 'but that's ridiculous. It would be more correct to say that he had no professional life, since everything he did was personally done.' Actually, this is a rather good description of Michael Herr.

Herr works in a bat-cave. His office is a tiny room in an otherwise spacious house amid the rolling hills of upstate New York, a dark corner in a home otherwise bathed in natural light. The 'office' walls are piled from floor to ceiling with music and books. Wagner, Mozart, Coltrane, Monteverdi and Shostakovich climb up one wall, while Kierkegaard, Cicero, Austen, Nietzsche and the Russian classics fight for shelf space up three others. 'And you know what?' he says with a grin. 'I could throw it all away tomorrow and not notice. I am cleaning it all out. Cleaning everything out.' That is both the beginning and the end of the conversation, also the point of departure along his long road to meeting, and now writing about, Stanley Kubrick. The road to Full Metal Jacket that begins in Vietnam.

Herr went to Vietnam 'as part of the decade thing. I had done the decade, and it had to end in Vietnam'. He had moved to Manhattan from his home town of Syracuse, to a teeming Greenwich Village where he commuted between his apartment and Bill Graham's Fillmore East rock venue: 'Jimi Hendrix, Jefferson Airplane and everyone except the Beatles.'

He wrote for the pioneering Holiday magazine, also famous for the work of Hemingway, Faulkner, V.S. Pritchett and Saul Bellow. But it was for Howard Hayes's then trail-blazing Esquire that Herr went to South-east Asia. One soldier asked Herr if he had 'come to report on what we're wearing'. 'I needed the accreditation,' explains Herr, 'and Hayes was okay with that.'

Every writer who has tried his or her hand at war journalism (myself included) would go to meet Michael Herr rather like a student of the cello would approach Mstislav Rostropovtch. Apart from learning by listening, the gratifying thing is to find that one's own follies and fears are echoes of Herr's; one almost feels validated in one's quirks of judgment in the aftermath of war.

One of the tortures of covering war in Bosnia was the necessity to surrender one's detachment and neutrality, supposed bedrocks of the journalist's trade - it was considered grossly unprofessional by some for me to testify at the war crimes tribunal in the Hague, for instance. But Herr is quick and unequivocal about the confluence between seeing and acting: 'You cannot be detached. If you are, you don't get it, however much you want to be a pure observer. If you are neutral, you don't understand it.'

Another problem in Bosnia was the creeping realisation that the media are impotent in the face of political cynicism. A daily diet of concentration camps, rape camps, ethnic cleansing, bread-line massacres and water-queue massacres did nothing to affect the politicians' resolve to do nothing but bleat broken promises. Herr's war, however, was supposed to be the model for the kind of news reporting that moved public opinion into sabotage on the home front. But Herr takes a heretical, opposite view.

'Television and news were always said to have ended the war. I thought the opposite. These images were always seen in another context - sandwiched in between commercials, so that they became a blancmange in the public mind. I think if anything, the blancmange coverage prolonged the war.'

War correspondents like to hang out together, for obvious and estimable reasons. Ancient mariners are comfortable with each other, since there is no need to press the wedding guest to the wall and endure the exhaustion of telling the tale. But the mariner-correspondents divide between those who return to the 'theatre' for whatever reason and those who cannot face it. For what it's worth, I was always among the latter; I never went back to Bosnia, and thought this a failing.

Herr tells a funny story out of the blue: 'I was always being asked to go to Vietnam and to functions and reunions. I never went. They invited me to the dedication of the Vietnam memorial in Washington DC, and I declined. I later went by myself and found it dynamic and very, very emotional - always someone there in sun or snow, day or dead of night, pointing out the name of an uncle to some kid. And once I did go to a reunion of war correspondents, a kind of uptown American Legion night. Terrific to see everyone; lovely evening. But you know? I was the only person who had never been back to Vietnam, and I never would go back to Vietnam. It wouldn't be a good thing for me. I still feel the elephant grass every time I hear a chopper, but please, not all that Robert McNamara stuff, crocodile tears and mea culpa in that creepy way. Or else Oh! What A Lovely War . What crap.'

Herr liked and likes the Vets, even those who are 'not incredibly bad guys but who did incredibly bad things'. He followed, and is angered by, the treatment of the veterans upon their return - those kids of 19 from the prairies and ghettos of America sent to a place where they expected to find a McDonald's and instead found insanity. Those who then returned when they were 21, despised by the liberals for having gone and by the establishment for having lost.

'There were more suicides among the vets,' says Herr, 'than were killed in the war. They were off the chart. There was no welcome back from their own people and they were spat at by the hippies. There was no recognition of what had happened to these guys.' And yet he is merciless with those haunted veterans who still sit wearing sunglasses at the back of bars in the rust belt, at three in the morning, if they have not yet taken their own lives. 'You get what you deserve in the end. Those men who came back and beat up their wives, who can't clean it out,' muses Herr. 'They are in the hell realms they deserve to be in, where people are tortured maybe not by what they have done, but by the fact that they may have got some pleasure out of doing it.'

Why, after all that, Michael Herr, are you not crazy? He stares out from the bench across the lawn over which the branches reach, laden with high summer, and answers with a naked honesty that is almost scary: 'I did go crazy. The problem with Vietnam is that if your body came back, your mind came back too. Within 18 months of coming back, I was on the edge of a major breakdown. It hit in 1971 and it was very serious. Real despair for three or four years; deep paralysis. I split up with my wife for a year. I didn't see anybody because I didn't want anybody to see me. It's part of the attachment. You get attached to good things; you get attached to bad things. Then I decided to look the other way. Suddenly I had a child. I went back to my book.'

Most of Dispatches had been written over the 18-month period before Herr's depression. And when the book was published, he says: 'I was famous for a while. I was always ambitious and I always wanted to be famous. And now I was. I had money. The writers I admired were now friends of mine such as William Burroughs, Salman Rushdie, Philip Roth.' Out of the comfortless landscape of Dispatches , then, came happy years raising a family off the Old Brompton Road in London. Then, in 1978, Apocalypse Now , with Francis Ford Coppola. 'I loved doing that. I was uncertain about returning to the Vietnam thing, but it was a wonderful experience, and of course did more good for my vanity and ego. But after that, that was it. No more Vietnam.'

Kubrick and Herr met in 1980, when the director was deliberating the idea of a film about the holocaust, and wanted Herr's view on Raul Hilberg's epic The Destruction of the European Jews . But Kubrick's real target was obvious. Not Dispatches - there was insufficient narrative - but Vietnam, certainly. 'He didn't want to make an anti-war film,' Herr says, 'he just wanted to depict war. He wanted to show what war is like.'

'Doesn't that remind you of someone?' I ask.

'Er, yeah. Suppose it does.'

An ideal match, maybe, but it took Kubrick three years to persuade Herr to return to his 'hell realm' of 'Nam. 'I once described 1980-83 as a single phone call lasting three years, with interruptions,' writes Herr. 'I'd think DOESN'T THIS GUY GET TIRED?' The Vietnam book that both Kubrick and Herr settled on was the one which Herr himself places above all others, and which is now 'outrageously out of print' - The Short-Timers , by Gustav Hasford. Hasford was, by Herr's own description, 'a scary man, a big, haunted marine', whom Kubrick was determined to meet. 'I advised him against it,' recalls Herr. 'I told Stanley I didn't think they'd get on.' Kubrick insisted, Hasford duly came over to Britain and there was a dinner during which Kubrick passed Herr a note saying: 'I can't deal with this man.' From then on, Hasford was dismissed from the maestro's presence. The movie, however, went ahead, famously bearing all the hallmarks of Kubrick's genius and Herr's inimitable insight into the vicious humour and the relentlessness of war. It is not, however, Herr's favourite Kubrick film, a pride of place he reserves for Barry Lyndon .

Herr's book is too restrained to admit it, but Kubrick clearly adored his American friend. He protested wildly when Herr elected to return to America. But they kept in close contact and from their collaboration came this book, which is a welcome retort to the absurdity from Frederic Raphael about Stanley Kubrick the 'self-hating Jew' ( Eyes Wide Open , published last year).

There is an intriguing point about Kubrick's 'ear' rather than his endlessly analysed 'eye' - about Kubrick's sensibility towards language. 'The basis of our friendship was verbal, not visual,' Herr recalls in conversation. 'Kubrick was drawn to language, he loved language. It was not the message of A Clockwork Orange that lured him, it was the language in the book. His method was to capture the visual equivalent to language.'

Then there is a point about Kubrick and music. Everyone knows that Kubrick used music like no other director outside the old USSR. Herr develops the theme in his book, but sadly omits a story about how in 1984, during the making of Full Metal Jacket , Kubrick asked him: 'Did you ever hear the Rolling Stones?' Kubrick clearly had not, even though Mick Jagger invited himself to dinner chez Kubrick after seeing Clockwork Orange . Kubrick's explanation was that he had been 'too immersed in Beethoven and the Strausses while making Orange and 2001 to notice rock and roll'. As everyone knows, 'Paint It Black' makes it big into Full Metal Jacket . Being famous, says Herr, 'was wonderful. Then it was not so wonderful'. Why? 'Suddenly enough was enough.'

Paint it black. It's funny talking to Herr. That unnerving certainty. That quiet core. I find myself talking about things I really shouldn't. About how I, for what it's worth, still have the nightmares; and about how sometimes when the phone rings, I smash it. 'Hmm,' he says, 'sure gets worse 'fore it gets better.' Have to replace the phone a lot. Smash crockery. Shout at people I shouldn't shout at. Can't sleep. Michael Herr doesn't do that kind of thing any more; he demobilised to some other zone. How?

It was while he was 'famous' that Herr decided to 'look the other way' once again. This time towards Tibetan Buddhism. His commitment is absolute. He meditates; he thinks; he is immersed. He gets up at six in the morning, but is unavailable to anyone until 10.30. 'I am not qualified to talk about this,' he insists, infuriatingly. 'I am not a Lama, I am a novice. But I know this: that whatever you are dealing with is real all right, but what you do with it is in your mind. That is the upside to the attachment, to not being detached. You take responsibility in your own mind, and that is how I cleaned it all out. It all happens in your own mind.' And he pulls the peak of his baseball cap down over his forehead.

 Kubrick by Michael Herr is published by Macmillan at £10.