Eight years after the publication of Trainspotting, even the serious critics are taking Welsh seriously. The New York Times review of Glue described him as an “unflinching contemporary Dickens.” Some are more grudging with their praise. “Having exhausted all possible genres,” opined the deputy editor of Prospect magazine recently, “you are left with only one weird conclusion: Welsh writes literary fiction.”

Still, you get the sense that this critic is grasping at straws, as was the woman who wrote a Web-published doctorate on the use of dialect in Welsh’s work, and who was reduced to such assertions as, “To shag means to have sex with someone.” Despite the reams of expert analysis published about him, Welsh remains an enigma, and not only when it comes to his work.

IRVINE WELSH is notoriously reluctant to speak about his personal life. We know he was born in Edinburgh, in 1959. We know he spent some of his childhood in the schemes, and that he took on a number of dead-end jobs — TV repairman, furniture mover — before moving to London in the late ’70s, where he hung around on the fringes of the punk-rock scene, did drugs, and dabbled in higher education. We also know that Welsh made a bundle in the mid ’80s by buying London properties, fixing them up, and flogging them at a tidy profit. We think he might be married. We’re pretty sure he has no kids.

Thanks to the voracious appetite of the British press — and Welsh’s penchant for self-promotion — we know a good deal more about the author’s social life. He’s become a familiar face on the European club circuit (as a DJ and floor-hopping patron) and a vigorous defender of the club drug ecstasy (which has earned him the dubious moniker “poet laureate of the chemical generation”). He has his own band, the Hibees (after his favorite soccer team, Hibernian), and a few years back teamed up with the British band Primal Scream to produce a hit single. He is, as he never tires of telling us, just one of the lads.

But you can’t stay a lad forever. Welsh is 42, and in April he behaved exactly as you’d expect a hard-living 42-year-old to act: he abandoned his club gear for a track suit, and ran in the London Marathon. “For a month it was no cigarettes, no drink, no drugs, no tea, no coffee,” he says. “I felt great, but I was boring. I was really tedious. But I felt like the year before that I was getting a bit too fucked up on the drink and the drugs. I was getting boring in a different way.”

You cannot be a lad forever. This is the basic premise behind Glue. Knowing Welsh — the man who published books called Ecstasy: Three Tales of Chemical Romance and The Acid House — you hear the word “glue” and you think “sniffing.” But the glue of the title is less a celebration of the psychotropic qualities of adhesive than it is an exploration of the bonds — loyalty, shared history, community — that hold four neighborhood friends together.

The four friends in question are Terry, a sex-mad, light-fingered clod; Gally, a sensitive boy who lacks the strength, or ruthlessness, to survive scheme life; Billy, a hard-headed boxer; and Ewart, a DJ and ecstasy nut. On the surface, these are familiar Welsh figures, but they are actually unlike anything he has created before, if only for the reason that the characters in Glue grow up.

Indeed, though much has been made of Glue’s resemblance to Trainspotting, the book represents a great leap forward for Welsh. Generally, his novels adhere to a single principle: “You get a character and make them deal with something really extreme for a short period of time.” In Glue, the action spans three decades, from the 1970s to the new millennium. The book is 469 pages long. A big book. An epic. “A pain in the arse,” says the author.