Much like the infamous "lost" 21st chapter of Anthony Burgess' novel A Clockwork Orange, Irvine Welsh's new Porno is likely to polarize fans: Some will argue that it unnecessarily expands the boundaries of a self-contained story, while others will find it a welcome continuation of a narrative that otherwise ended too abruptly. A sequel to Welsh's debut novel Trainspotting (which, like A Clockwork Orange, was harrowing, fascinating, and so slang-heavy that it needed decoding as much as reading), Porno returns to Scottish scrabblers Mark Renton, Frank Begbie, Simon "Sick Boy" Williamson, and Daniel "Spud" Murphy, roughly nine years later. Having fled the country with the proceeds of a once-in-a-lifetime drug deal, stolen from his semi-friends at the end of Trainspotting, Mark is now the part-owner of an Amsterdam nightclub. Begbie has just been released from jail, and seethes with the psychotic need for violence, particularly toward the long-gone Mark. Spud, like the rest of his erstwhile junkie pals, is off heroin, but he still frequently uses speed, alcohol, and whatever else can dull his self-loathing. And Sick Boy, the book's most prominent character, returns to his reviled Scottish hometown to take over his aunt's pub, but he still buzzes with get-rich-and-famous-quick schemes, from a false-front anti-drug campaign that gets his name in the local papers to the amateur pornography he plans to film in the pub during off-hours. Porno's point of view alternates between these characterseach represented by a different flavor of Scottish dialect and slangand adds a fifth perspective, that of attention-hungry, sexually voracious Nikki Fuller-Smith, who grabs Sick Boy's attention, among other things. As the novel's central antagonist, Sick Boy is pretty small-time: His misogyny, racism, monomania, hypocrisy, and chronic cocaine abuse are deplorable enough, but the way he predictably betrays his allies within moments of any success makes him into little more than a Saturday-morning supervillain. His sociopathic machinations manage, just barely, to hold Porno together, though Spud tends to wander off on his own and Mark is just barely in the picture. Which is regrettable and a bit disturbing: Of all Trainspotting's aggressively aggrieved losers, he seems to have come the farthest socially and emotionally, but the more potentially redemptive his story becomes, the further he retreats into the background. It's as though Welsh loses interest in any character who's not suffering or causing others to suffer. There's plenty of suffering in Porno: Sick Boy hates everyone who stands in his way, Nikki hates anyone potentially more successful or attractive than her, Spud hates himself, Begbie hates everyone but himself, and all of them tear themselves and others apart as a result. But for all the involving emotion and energy, Porno ultimately does little to advance its story; Welsh's writing style has matured significantly over the past decade, but while he's moving forward, his characters are still circling the same familiar drain. At least chapter 21 of A Clockwork Orange let Alex begin to grow up.