Irvine Welsh: being a 'sadist'. Photograph: Murdo Macleod for the GuardianAs we've come to expect from an Irvine Welsh hero, Lucy Brennan, the narrator of The Sex Lives of Siamese Twins, is an unrepentant sadist and narcissist. A fitness trainer in the bikini-clad, ab-obsessed world of South Beach, Miami, she becomes an unlikely hero when she disarms a gunman who has chased two men in front of her car on the highway. Lucy's exploit makes her a star on local news – and inspires infatuation in a witness to the incident, the overweight, pathologically lonely Lena Sorensen. Lena tracks Lucy down the following day to schedule a personal training session.
At this point, the reader anticipates a stalking narrative. And when Lena turns out to be an artist who constructs distorted human figures from animal bones, our suspicions seem to be confirmed. But it's Lucy who gradually becomes obsessed with Lena, and specifically with carving the fat off her body. When Lena continues to gobble key lime pies on the sly, Lucy's tactics become increasingly abusive, while her interest in Lena grows perversely sexual. At last, losing patience, she drugs Lena and imprisons her in an empty apartment building. Fed by her captor on blueberries and protein shakes, with only a treadmill and a home gym for company, Lena at last loses weight. She is chained to a pillar, she is defecating into a bucket – but she looks fantastic.
As a concept, this is brilliant. It powerfully encapsulates the book's themes of body obsession, co-dependency, and the American cult of willpower. And, for anyone who's ever tried to diet, it's a twisted wish fulfilment fantasy. But the pleasure of the book is spoiled by a radically misjudged narrator.
Welsh has a history of testing the limits of his readers' capacity for empathy. No one can write about a sociopath in love with so much heart. But his Lucy not only lacks any sympathetic qualities, she lacks any interesting qualities. She has one-night-stands with people she despises and mistreats; personal training sessions with people she despises and mistreats; lunch with her mother, whom she despises and mistreats. Here, all overweight women are beachballs, lard-asses, blimps. An older woman is a "crinkled, leather-faced, old scrotum". Whatever else they are, women are bitches. In a typical passage, Lucy describes the Democratic and Republican candidates for governor: "Thorpe is a well-meaning but flatulent-mouthed, carpetbagging Ivy League asshole, while Quist is a rabid, fascist, sanctimonious, Bible-bashing prick ... It's hard to work out which one I hate the most." When the venom recedes, we're left with passages like this: "Sorenson weighed in at 197.5 ... I decided that I was going to cardio her ass and burn shit off her. I started her on the elliptical, and doing a 4 x 15 minute workout, increasing the resistance level from 8 to 10 to 12 to 14." Meanwhile, in his rendering of American speech, Welsh succeeds a little too dramatically. He conveys not just American English, but the way American English can grate on the English ear. And it does grate, and continues to grate, page after remorseless page.
Of course, it's reasonable to suppose that a South Beach fitness trainer would tediously count calories, itemise her meals, and assess every passerby on his physical appearance. And presumably there are some people whose responses to others are uniformly hateful. Some Americans really do abuse the English language. But choosing to write a 460-page novel in the voice of such a person is crossing a line. Welsh is not just portraying a sadist here; he is being a sadist.
As the novel progresses, Welsh introduces Lena as a secondary narrator. Lena is certainly less loathsome than Lucy, and she's convincing as a Midwestern girl who loves Cute Overload and doughnuts. But she's too leadenly ordinary to be credible as the world-class artist we're told she is, much less as the focus of a stranger's erotic obsession, while her bovine capitulation to Lucy's bullying doesn't seem to be grounded in anything but the author's convenience.
Ultimately, this novel is simply frustrating. Its plot is not only cleverly conceived but genuinely, hauntingly, transgressive. It could have been a powerful and profound book, with just a bit more thought. One reads it wishing vainly for Welsh to humanise some of Lucy's reactions; to motivate some of Lena's decisions; to allow any character the range of expression of Welsh's best creations. Most of all, The Sex Lives of Siamese Twins would have been a great, page-turning read if it were narrated not by Lucy and Lena, but by someone with the intelligence and expressiveness of Irvine Welsh.
• Sandra Newman's The Country of Ice Cream Star will be published by Chatto in June
