"i'll sleep when ah'm dead, ya know?" Irvine Welsh is sitting unrecognized on the dark steps that lead up to the pool tables at the San Francisco club Deco, a gritty Tenderloin District retreat for ravers and stoners -- both of which could define Welsh at this moment. Awake for more than 36 hours, amped on ecstasy and alcohol, the Scottish author of "Trainspotting" and other dark novels of Scotland's drugged-out underbelly is in a bit of a slump. He rubs his shaved head like a contented Buddhist, tries to focus his eyes, manages a wobbly smile. "Nah, I don' need sleep just yet."

Alan Black, the head of San Francisco's thriving Scottish Cultural and Arts Foundation (no kilts here -- just revolutionary plays, music and literature), is a mate of Welsh's. He witnesses this bacchanal each time the 37-year-old author's in town. No cause for alarm. "He'll get his 10th wind pretty soon, you'll see," he chuckles. Sure enough, Welsh steadies himself and soon is seen in the DJ's corner, spinning platters -- something he does all over London when his busy life allows. Next stop: the 11th Street club corridor, an after-show party for the Chemical Brothers, more celebrities on Welsh's endless list of pals. I have to beg off. I didn't do any ecstasy and mere mortal energy is exhausted. I've been trying to keep up with Welsh for two days -- a blurred period that will forever after be known as the Lost Weekend of the Great Scots tour.

The four-city book-flogging junket was set up by Norton Books to showcase Welsh (whose most recent novel is "Marabou Stork Nightmare"), rising young lit star Duncan Maclean ("Bunker Man") and the venerable and incisive James Kelman (who won the Booker Prize for "How Late it Was, How Late"). The carpet had been unwittingly rolled out for the visiting Scots by the British electorate: The night before the authors' arrival, every Tory in Scotland was getting his ass kicked and the mood was ripe for revolution. At Edinburgh Castle, a pub that's the hub for the city's sizable Scottish population, punters howl at the good news. Black and his cohorts hurl limes at the TV screen every time a deposed Conservative appears. "Fuckin' right-wing hypocrites," Black growls.

The next night, Saturday, the tall and slender Welsh makes his way through the sweaty, packed crowd of hipsters, who crane their necks to see The Man. Welsh, who is there with Kelman and Maclean to do a reading, thrills them by doing, for the first time in years, a selection from "Trainspotting" -- the notorious scene where Spud "messes himself" in his girlfriend's bed, wraps the mess in the sheets, then haplessly catapults the assorted bodily fluids onto her parents at the breakfast table. Leaning into the microphone, looking up at dramatic moments, Welsh reads brilliantly.

Chatting later over a Guinness, Welsh beams. The tour's been great, he and the other lads are getting on famously. The only sticking point: his own hedonist tendencies. "I'm tryin' to be good. Duncan is quite wholesome and hearty, and Jim is pretty dignified. I don't want to be the bad apple who drags their names through the mud!" Soon after this, Kelman and Maclean depart, leaving Welsh to his own devices. He proceeds to belly up to the bar numerous times, greeting fan after fan warmly as he goes.

The event's other purpose was to launch the Scottish Cultural and Arts Foundation's new online zine, Razor's Edge, which bolts from the gate with short stories by Kelman and three other promising Brits. Asked if his infamous Q&A with Rebel Inc.'s Kevin Williamson, during which they both took ecstasy and recorded their sensory impressions in a hilarious, rambling dissertation, will appear in "Razor's Edge," Welsh laughs. "I dunno, maybe! You know that was the first time Kevin took it. I had to ram it down his throat!"

Welsh, raised in the projects, seems to be always amused by life and fearless of its consequences. He had nearly missed his plane in New York City the morning before, after being up all night with a Scottish comedian. "Yeah, I was kinda fucked up," he shrugs. "We went down to the Lower East Side and ended up at what was basically a crack house. It was pretty wild. And I didn't get any sleep. But I made it!" he says cheerfully. I wonder what his publicist thinks of his candor about his fondness for all things illicit. An appearance on National Public Radio's "Fresh Air" was vintage Welsh. He offered responses like, "If you came from a certain place at a certain time, you couldn't help being part of the (drug) culture, in Edinburgh especially. The behavior was archetypal; if not heroin then it was alcohol." Later in the broadcast he joked about someone being a "smart cunt." The censor didn't catch it. "Hey!" he protests later, "They said no 'fuck' -- nothing about 'cunt.'"

If Kelman and Maclean resent being upstaged by Welsh's audacious behavior, they keep it well hidden. All are good friends; all are beneficiaries of the world's current obsession with Scottish writing -- jump-started when Kelman won the coveted Booker and "Trainspotting" changed the way British young people related to literature. Lured by tales of spat-upon junkies thumbing their noses at the world, copies of "Trainspotting" were passed hand-to-hand at raves and sold on record store counters. Suddenly, video-holics were discovering books could be, as Kelman described it, "a relevant art form."

All three are embarrassed by the "Great Scots" title attached to their tour. The 50-year-old Kelman, who does not suffer idiocy gladly, says that to emphasize the Scottish national angle "is to continue to marginalize the culture." Welsh, bucking the solemnity, has his own spin: "My idea of a 'great Scot' is Scotty on Star Trek!"

By the end of the Edinburgh Castle gig, Welsh has hooked up with his local friends and danced himself into sweaty exhaustion. Of course, it's only temporary. He stretches out on the covered pool table, grins. What's next? he asks. They slip out into the night.

The following evening is the weekend's most formal appearance -- a reading and panel discussion at the Cowell Theatre -- and Welsh has not slept at all. He is bleary-eyed with exhaustion. Halfway through, however, he straightens up and practically glows with alertness and wit -- the result of dropping a tab before going onstage. His reading selection: a depraved chapter from his novel "Ecstasy" (no irony there), dealing with the effects of crystal meth on one's erection. Before the oral dissertation, he tells the crowd, "This won't be my normal reading tonight; I'm off my tits." While a nervous chuckle ripples across the lit-hip crowd, he also offers: "People always ask me why I write so much about sex and drugs, but you write what you know."

The reading is fine, rich with characterization and humor. But when the crowd peppers the three authors with questions at the close of the evening, Welsh's sponsors and pals hold their collective breath. What do you think of the impact of the drug ecstasy on the young? he is asked. "Well, it's working pretty great for me right now!" he laughs. When asked why the working class is so underrepresented in literature, he offers a long and rambling discourse that does not satisfy the questioner. What does he really mean? "I MEAN," he emphasizes, "That books are written BY rich cunts FOR rich cunts." Then he laughs, and the audience laughs with him.

Sometime later that evening, in the dark confines of Deco's architecture, Welsh ponders the weekend. "I fuckin' love it here. I always have a good time. I mighta done a little too much this time, though."