A "happy number" is a number in which the iterated sums of the squares of the digits terminate at one. You don't have to understand such things to enjoy Keeble's third novel, which combines East End gangsters, coincidence and parenthood to pleasing effect. Miles is a hulking statistician at the Royal London Hospital who boils his potatoes for exactly 13 minutes, eats his crumpets in precisely 45 seconds and has all the social skills of a maths textbook. His existence is shaken when he heads next door to warn his tenant about unpaid bills and finds her corpse bleeding on the floor. To him it seems like a ghastly accident, but to his guardian angel Felicity, a mysterious transsexual who blends into street corners and drinks fortified cider, there's something fishy afoot. Keeble's sharp eye brings London's multicultural streets to life, and while the action  in which themes are flung together with great enthusiasm and moderate dexterity  isn't always as credible, this is a big-hearted, readable little book that whips you along merrily.