The Bedroom Secrets of the Master Chefs by Irvine Welsh

Irvine Welsh got married last year. The high priest of the chemical generation concedes that re-initiation into that bond - 25-year-old Beth Quinn is his second wife - has given him, "a new outlook". Ecstasy is out, green tea is in. These facts seem to resonate within Welsh's first novel since Porno in 2002. The Bedroom Secrets of the Master Chefs is a Jekyll-and-Hyde-esque narrative of duality in which the two central characters move in demonic orbit around one another; one is a clean-living and fastidious family man, the other a cocaine-fuelled hedonist.

There's plenty of room for Welsh to report from the usual terrain; his native Leith, the pub and the gutter, sex and violence. But more unequivocally than any previous Welsh novel, Bedroom Secrets is a work in pursuit of metaphysical as well as representational truths. Its real terrain is the soul. But time and again Welsh finds himself caught between narrative realism and the magical parable that he wants to tell.

An awkward narrative structure is one symptom; one quarter of this book is over before Welsh introduces the key plot device. At Edinburgh's Department of Environmental Health, hard-living Danny Skinner is sinking into alcoholism, tortured by his mother's refusal to reveal the identity of his father. He suspects the answer may lie with Alan De Fretais, an egotistical local celebrity chef and author of Bedroom Secrets, a guide on seduction and food. When fresh-faced Brian Kibby arrives at the department, Danny finds himself consumed by a seething hatred of his clean-living rival until, during a drunken and vitriolic interior rage, he enacts a hex. Now Danny can drink, fight and snort with abandon and Kibby's body, not his, pays the physical toll.

We are propelled on a tide of black voyeurism across the ever more potent humiliations Welsh devises for Kibby. "Fuck knows where the fuck this is gaun, but I've got Kibby tae take the negative shit," thinks Skinner before a particularly grim scene, in which he is anally raped. But already this novel is signalling its failure to us. Where in Trainspotting that sinewy, muscular Scottish vernacular for which Welsh is renowned seemed to grant us the eyes of Renton and Sick Boy, here it is a tacked-on device, erratically deployed. One minute Danny is deep in vernacular, the next he tells us: "My troubling speculations are broken by..."

The incoherent characterisation extends beyond language and to the heart of the book. Welsh is slipshod in his attempt to incorporate a supernatural moral polemic into this otherwise naturalistic novel. He wants us to believe in Brian and Danny as real people in a real world, but also to usher them through his argument with a minimum of fuss. So when Danny burns his cheek and a mark appears on the cheek of Kibby, the latter visits a doctor who says with miraculous clairvoyance, "this mark on the cheek, it's like a cigarette burn of that type that might be self-inflicted."

Only when Welsh cuts his characters temporarily free from responsibility to his plot can he make them blossom into life. And all the time the search for Danny's father lurches in and out of view, as though Welsh doesn't quite know what to do with it. It all means that although Bedroom Secrets sets its sights on fascinating themes - the creative and destructive aspects of our natures, the Faustian pact we unwittingly strike with those around us - its characters are made mere puppets attached to visible strings, and we cannot care about them.