In Lifeless, Mark Billingham's Tom Thorne reaches something like the nadir of his police career, broken by the death--possibly the murder--of his demented father and shuffled off to a desk job of infinite tedium. When someone starts kicking the London homeless to death, he suggests going undercover, and those of his friends who care about him worry that he is looking for his own destruction as much as for the killer. Certainly Thorne finds compensations on the street for danger, cold, hunger and squalor--his friendship with two young addicts is nonetheless real for his deceit and their pragmatic ruthlessness. Yet the secret of the deaths he is investigating lies only partly in London's dark alleys and corners; it lies as well fourteen years in the past on the road to Baghdad... This is probably Billingham's best thriller yet--inventive and passionate and full of commitment and dark humour. In his vulnerability and shrewdness, Tom Thorne is gradually shaping up into a classic detective whose habit of breaking the rules is not so much a strength as part of a pattern of self-destructive behaviour. Billingham's writing gets better with each book, too--the rough tenderness for each other of Spike and Caz, Thorne's mildly deranged guides to the street, is delicate and moving. ---Roz Kaveney