There is no place in literary fantasy as strange as the multiple layers and many cultures of a modern city, seen asquint. This is why, from Moorcock to Gaiman and Mieville, some of the best British fantasy has not dealt with the great Matter of Arthurian Britain, but the Matter of London. Such novels not concerned with heroic quests for the cure for the world's pain so much as the equally huge problem of making a place for human life amid blood, money and filth. China Miéville's first novel, and his first book for young adults, were both stabs at this subject - all his books are, if you see New Crobuzon in the three "Bas-Lag" novels, and the divided Beszel/Ul Qoma of The City and the City as versions of London, just as much as the Invisible Cities of Italo Calvino are all Venice.
The London of Kraken is a site where multiple beliefs contend and there is a section of the police whose job it is to hold cults under control in case one actually does have the power to bring about the version of the Apocalypse to which they adhere. The theft of a pickled giant squid from the Natural History Museum is the sort of magical event that interests them, but not as intensely as it involves Billy, the expert who oversaw its pickling.
He suddenly finds himself a player in a world of assassins and crusaders and inquisitors of whose existence he had no idea. Billy finds out the hard way that you don't have to be a peasant boy, or a hobbit, to find yourself at once the most important piece on the chessboard of the world, and the idiot child who has to learn to ask the right questions.
The great strength of this book is Mieville's understanding of belief as a way of life: the multiplicity of cults that live together in his world, only occasionally turning on one another in frenzy, have, as one would expect from his left-wing political background, more than a passing reference to the multiple versions of Marxism/Leninism. As in his other books, he presents violence as the way that different truths compete for supremacy. The smartest person in the room is going to also be the one who uses mayhem most efficiently.
In the end, this is a bleak book because Billy will never quite be able to go home again. He thought that he lived in the shiny world of Time Out's best bars and restaurants, but he discovers that the truth is a world of danger, of gangsters who exist as tattoos and bad men who swallow you whole. It is this emotional truth - knowledge is power, but it is also pain - that makes this excellent urban fantasy transcend its occasional moments of enjoyable silliness. Billy may, from time to time, win by reversing the polarity, but only because he acquires real, and not just magical, wisdom.
Roz Kaveney's 'Superheroes!' is published by IB Tauris