The Sex Lives of Siamese Twins by Irvine Welsh, book review: This new novel is a return to top form for the 'Trainspotting' author

The thing about being the voice of a generation is that every generation grows up. Few authors will be more acutely aware of this than Irvine Welsh, whose explosive entry to the literary scene with 1993's Trainspotting and its subsequent screen adaptation by Danny Boyle into the stylish (strangely so, given its subject is heroin abuse in the housing schemes of 1980s Edinburgh) movie companion to the Britpop era has given him a mountain to climb in terms of sustained career impetus.

To his credit, he's kept going, even as Trainspotting's success might have allowed him to become a kind of gruff Scots analogue of JD Salinger or Joseph Heller, a one-classic wonder whose timeless reputation has been sealed by their earliest work. While it's true there have been further works well worthy of note in Welsh's canon – brutal fantasy Marabou Stork Nightmares; self-consciously grubby police procedural Filth; certain of the short pieces in The Acid House and Ecstasy – returns have diminished as his career has progressed.

Porno (2002) and his most recent novel Skagboys (2012) were a less well-received sequel and prequel, respectively, to Trainspotting; Crime (2008) was a less well-received sequel to Filth; The Bedroom Secrets of the Master Chefs (2006) was the most badly-reviewed of all his books, not undeservedly. That this latest novel shares a similarly tabloid-styled title as the latter might put many off, but that headline-grabbing top line disguises an unexpectedly confident return. It's ironic that even as the recent film adaptation of Filth reintroduced his affinity for sweary, degenerate Scottish troublemakers to popular culture, The Sex Lives of Siamese Twins for the first time takes a strong and convincing grip on voices which sound far removed from those of the Muirhouse scheme in which the author grew up.

Welsh's current biography places him in Chicago with his second wife, but his Twitter profile lists his other residence as Miami, Florida, and it's there that Sex Lives is set. It pits both self-images of America against one another – Lucy Brennan in one corner, frighteningly focused workout Nazi at Hardass Training and "somebody to shake America right out of its complacency", whose subduing of a young man chasing two individuals across the Julia Tuttle Causeway with a handgun makes her a local cause célèbre, in a Hollywoodised inversion of The Bonfire of the Vanities. In the other, Lena Sorensen, artist and frequenter of cute animal websites, her confidence crushed by a psychotic ex-boyfriend and her presence "a crime against the aesthetic order in South Beach", according to Brennan.

It's Sorensen who films Brennan's actions on the interstate, first turning her into a celebrity and then into a villain when it emerges the man was out for revenge on two paedophiles who abused him when he was younger.

Yet her actions cement the pair's relationship, as the brutally blunt and image-consumed Brennan first unwillingly agrees to be Sorensen's personal trainer, and then becomes obsessed with correcting her overeating behaviour to the point she kidnaps and imprisons her. Throughout, the story of two conjoined twins and their planned separation plays out in overheard news media, a reflection of the fatal symbiosis the duo have entered into.

With a cast of characters poised between humanity and grotesquery, and the exposure of some extreme behaviours which are no less apparent than during some entirely pornographic sexual encounters, this is unmistakably Welsh, and many readers might not appreciate its sensational veneer.

Yet how far he has removed himself from his comfort zone in writing female Americans is validated by the clarity with which he eviscerates Western society's great – and potentially most dangerous – obsessions with food, health, sex and emotional perfection. At the age of 55, he's also at last produced proof he can write convincingly about experiences suitably removed from his own.