One may as well begin with the end. I have just had a three-hour lunch with Jay McInerney, a man who made literary history on the back of a good time. As he tells me euphemistically of the 1980s New York restaurant scene documented in his first novel, Bright Lights, Big City: 'There was a lot of not-eating that went on.' McInerney is now 50, and though his habits may have changed, it would seem that his appetites have not. After three courses and countless complimentary petits fours, I stagger to the front of one of the best restaurants in Manhattan with the thought that I need not eat again for another three weeks. But when I look up, McInerney has beaten me to it. There he is, chatting to the maître d' and booking himself into the same place for dinner that very night.

On the phone, he had considered our venue options - something polished like the Four Seasons, where media moguls have personal tables? Or somewhere downtown and more cool - Soho House, perhaps? Eventually, he settled on a venerable institution about a two-and-a-half-minute walk from his apartment in Greenwich Village.

The day we meet, the Gotham Bar and Grill exudes a quiet, sexagenarian chic. McInerney arrives wearing a blazer and carrying a proof copy of Thomas Jefferson's writings on wine under his arm. He manages to look boyish, louche and eminent all at once. McInerney writes a wine column for American House & Garden magazine ('It's as if someone were paying you to date beautiful models and actresses,' he says of this sideline. His second collection of wine writing, A Hedonist in the Cellar, will be published in the UK this week.)

He sits down and glances at the menu. 'Oh! Well, heirloom tomatoes - while they're here, that's what we must have,' he says. Not one to disobey orders at this early stage of the meal, I ask for the tomatoes and the miso blackened cod. He does too. He insists on not drinking, muttering something about how he would never get any writing done if he did all the lunchtime drinking people assume he indulges in. When the waiter comes, he changes his mind. 'I just realised,' he says, turning to me with a sheepish smile, 'I have absolutely nothing to do today.'

McInerney looks around at the hushed lunchtime crowd. This, he explains, was one of the first serious downtown restaurants in New York. It opened in 1985. Judging by the towering presentation of the entrées, that's a decade from which it has yet to recover.

The uncharitable might say the same of my companion. Chloë Sevigny, an actress whose career took off when McInerney wrote about her in The New Yorker, has suggested he's 'a little out of touch'. Yet in person, McInerney reveals an effortless confidence. Though he will concede that 'there are always going to be 19- and 20-year-olds to replace the rest of us', he will also tell you that, unlike 19 and 20 year-olds, he can now get a table at a top New York restaurant at the drop of a hat. I notice that in conversation about the Eighties, he does not say 'when I was young'. He says: 'When I was a new star'. Sometimes, he suggests, he will be sitting alone at a bar reading a book and 'some Wall Street guy' will recognise him and pour McInerney a glass of his $2,000 bottle of wine. His guide to Manhattan eateries features a prominent role for himself. 'Per Se,' he tells me. 'Now there would be a reservation that would be very coveted. If you could, in front of your friends, get a reservation at short notice at Per Se ... You call and you say, "Laura? Yeah, Jay McInerney. Listen, I really ... there are four of us, I know it's late but we need a table at 8:30".'

'Sounds good,' I say, passing him my mobile phone. McInerney laughs. 'I mean, I have a better chance than most people. I just do.'

McInerney arrived in New York in 1980, the year that Keith McNally, New York's hippest entrepreneur, opened his first restaurant. Odeon, in TriBeCa, was an instant hit - McInerney, then an impoverished fact-checker at The New Yorker who would nurse a single drink at the bar all night and wait for the Mudd Clubb to open, met Andy Warhol, Julian Schnabel, Jean-Michel Basquiat, the Saturday Night Live crowd, David Byrne and the Talking Heads. Legend has it that John Belushi used to cook his own hamburgers in the kitchen. But, as McInerney says, it wasn't really about the food. 'My first seven or eight years in New York didn't have much to do with food or wine,' he elaborates. 'We were more interested in having fun and drinking vodkas and snorting cocaine when we could get it and staying up all night. It wasn't very conducive to fact-checking.'

He was sacked from his job and went to study creative writing with Raymond Carver at Syracuse University. While he was there, he wrote Bright Lights, Big City about the life he had left behind, and worked in an off-licence in the evenings. 'It was a sort of ghetto liquor store, really. We sold a lot of fortified grape juice, alcoholic specials. But the proprietor of the store was a Princeton grad who had high hopes that the neighbourhood would gentrify some day.' He read about the history of wine while he was at a loose end in the shop, and took home two-dollar bottles of wine, stealthily working his palate up to the five-dollar kind.

When Bright Lights, Big City reached its publisher, the legal department panicked: the artist had designed a cover that featured Odeon prominently, and there was a scene set in Odeon, in which cocaine is snorted in the bathroom. McInerney was instructed that he would either have to remove the scene or ask McNally's permission.

'So I went in and met Keith McNally. I didn't know him because I was such a hanger-on. I had no money, and I had no claim on anyone's attention. I explained the problem to him. He didn't really seem to care one way or the other, and didn't think he'd hear about the book again. So he said go ahead. At this point he thinks that I owe him a lot of money and I think that he owes me a lot of money: I think I helped put his kids through college, whereas he thinks I should be paying him royalties!'

MacInerney was the first member of what was later touted as 'the Brat Pack' of fiction writers (he was joined, in a way fashioned by his publisher for publicity purposes, by Bret Easton Ellis, Tama Janowitz and a rotating team of others). It was a time when the nightlife seemed, as he puts it, 'fresh and salon-like. I was sort of a spokesman for my generation and allegedly a symbol of the zeitgeist. It was a fun position to be in.' Then, at the launch party for Bright Lights in London in 1985, he was introduced to someone who would change his consumption habits forever: Julian Barnes.

'It was a great night. Bill Buford had just published this 'Dirty Realism' issue of Granta, so my friends Richard Ford and Tobias Wolff and Raymond Carver were all visiting. I met Martin Amis, Ian McEwan, Salman Rushdie, Julian, Hanif Kureishi ... For some reason the person I ended up staying in touch with was the unlikeliest one - because everybody thinks Julian and I are such an odd couple, and we are.'

Barnes had McInerney over for dinner. He served two Châteauneuf-du-Papes, a 1962 and a 1967 Jaboulet Les Cedres, two of the best wines McInerney had ever had in his life, and he was hooked. Entire filing cabinets' worth of faxes were then exchanged between them. Titbits of literary gossip were interspersed with notes on what they had drunk or bought. Oddly enough, they seemed to like the kind of wines one would expect of the other: Barnes liked what McInerney calls 'wines with cleavage', and McInerney's tastes were, oddly for him, more conservative. 'I realised that drinking with Julian was like playing tennis with a slightly superior player,' McInerney writes in A Hedonist in the Cellar: Adventures in Wine, his first collection of wine writing, 'the best possible way to learn and to sharpen your game.'

The meeting came just at the right moment. 'I think wine became a way of channelling my hedonism in more interesting ways - it was a way of intellectualising hedonism, if you will,' he reflects. 'Reading a lot of wine writing, you'd think that it wasn't actually an intoxicant, but it is,' he chuckles. For a long time, food was just 'a necessary evil'. One of his favourite combinations, for instance, is Krug with a large bowl of popcorn. 'I don't mean to imply there was a radical discontinuity between one kind of fun and another,' MacInerney emphasises. 'For a while they all blended together.'

The question is, aside from his own transition to finer things, is the party over? What's happened in New York since the days when he was the arbiter of the zeitgeist? McInerney is about to marry for the fourth time. His fiancée, Anne Hearst, is the granddaughter of the newspaper magnate William Randolph Hearst, and her daughter Amanda is one of New York's latest It-girls. Her life, as McInerney sees it, 'is all much more programmed and commercial' than it was when he was, as he puts it, an It-boy. 'I hate to sound like an old fart but it was much more spontaneous before. I mean, designers are sending her clothes every night that they hope she'll wear and be photographed in. Nightlife has been thoroughly domesticated and commercialised - like almost everything else in the time since I got to New York and we were making it up as we went along. I don't see anything now that hasn't been co-opted.

'I think one of the things that happened with people of my generation in New York in the Nineties,' McInerney goes on, 'is that, to some extent, restaurants did replace nightclubs, and restaurant-going became a kind of competitive sport. I mean, first of all, being able to get reservations in a particular place is an indicator of your position in the Manhattan social hierarchy. '

'Who competes?' I ask.

'Who doesn't? I mean, getting in to Babbo is a big deal, for almost anyone in New York,' McInerney says, referring to a restaurant that belongs to his good friend Mario Battali. 'Or being able to call Perry Street, Jean-Georges [Vongerichten]'s place, and being able to walk in that night. It separates a certain class of guy from another class of guy.

'The Four Seasons is a classic example,' he continues, warming to his theme, 'that's one that's endured for 30 years and, of course, so has the clientele. It's the same people. They still run New York, but they ain't getting any younger. It's like Henry Kissinger, Mort Zuckerman, Si Newhouse.'

Could being seen at the Four Seasons make someone's career, in gossip-column terms? 'Well,' McInerney replies instantly, 'as long as you're at the right table. There's three rooms, so first of all you have to be in the front room, and then preferably you're in the front section of the first room. If they put you in the second or third room, then you should probably just go somewhere else, because if your friends see you, they'll be talking about it.'

There is a brief pause before McInerney returns to the topic a little defensively. 'You think I'm making this up, don't you? I'm one of the world's living experts on this ridiculous subject! Because I cross more lines than most people - because I go uptown and downtown. Because I'm not only a scenester, I'm also a foodie.'

How could I think he was making it up? I say soothingly. The anthropology of such New York customs is famously entertaining, and if anyone has a handle on the tribal gatherings of the city's inhabitants, it's McInerney. He routinely sends his characters to real restaurants; in his latest novel, The Good Life, which relates the fallout for two families of September 11, lovers go to a dive in the Village for a tryst and a wealthy family has a chichi Christmas celebration at 21. I was only smiling, I explain, because I remembered a graph New York magazine once did, a sort of map of who sat where at the Four Seasons, and when they'd been promoted or otherwise.

McInerney knows the one I mean. 'The more interesting one they did, or maybe Vanity Fair did, was of Pastis when it opened,' he adds. Pastis is Keith McNally's bistro in the meatpacking district, a follow-up to Balthazar.

'Oh, I didn't see that map,' I tell him, 'What was it like?'

'Well, I didn't see it either,' he confesses. 'But a number of people told me I was in it.'

Though McInerney grew up all over the world - he lived in 12 or 13 different places as a child, following his 'corporate gypsy' father - he had, in his own phrase, 'a very pedestrian upbringing as an eater'. 'My mother was half-Russian, half-Irish Catholic - a disastrous culinary heritage. Not bad as a literary heritage, but we ate corned beef and cabbage, cubed steak and potatoes. I did not get my palate from my childhood. I remember when I was 12, we were living in Canada and we used to drive half an hour to experience this exotic new food which was called pizza.'

Now look how far he's come. He cooks dinner for 10 once a month (sometimes he even invites Mario Battali). When he lived in Tennessee with his third wife and their twins he used to get aged beef sent by FedEx from his favourite meat market in New York. And he now frequently sources truffles from Piedmont and has them shipped to him overnight. This is a man who remembers a time when he didn't know truffles were expensive. He took a girl out to lunch, said yes to the truffle-sprinkled pasta, and the bill blew his entire month's dating budget out of the water.

'It's funny the way cooking and gourmandising and epicureanism used to be seen as so effete,' he ponders. 'And now it's the province of red-blooded, brawny, sports-loving heterosexuals. I'm telling you, sometimes I hear my friends talking about the latest mushroom the way they used to talk about garage bands. I see guys talking about what the best knife is the way they used to talk about stereo equipment. So it ain't just me. Now cooking has come to seem like a masculine thing. Most couples I know, it's the man who does the cooking.'

For McInerney, cooking is a way to switch gears after a day of writing. He'll plan the wine in advance - he has to, because most of it is stored in a facility out in Queens, and they send it to him by the case. Nowadays, he even remembers the great events of his life according to the wine he drank on those occasions. The rest of the details will come to him only gradually. His first date is fondly recalled only after the naively chosen rosé springs to mind. Seeing the Twin Towers fall, he says, gave him 'more of a carpe diem attitude than ever. That night I opened the best bottle of wine that I had in the apartment - a 1982 Lynch Bages, with a couple of friends. I thought: "This could be my last."' The day he married his third wife, Helen Bransford, is memorialised by the 1990 Krug, followed by the 1982 Cheval Blanc and the 1982 Pichon-Lalande they had after the ceremony at City Hall. The fact that the wine is more salient than the wife may or may not have something to do with his being thrice-divorced.

I tell McInerney how astounding it is that he remembers those details so exactly. 'It's one thing I almost never forget,' he agrees happily. 'I can't remember my kids' names sometimes, but ...' He looks suddenly solemn: 'I'm joking,' he says.

· A Hedonist in the Cellar: Adventures in Wine by Jay McInerney is published by Bloomsbury for £14.99. Order a copy for £13.99 here