London keeps losing things. Broken umbrellas, dead milk cartons, words nobody bothers to say any more. They all wash up in UnLondon, a city assembled from the capital's castoffs and running on its own cracked logic.

Twelve-year-old Zanna and her friend Deeba find the way through, and UnLondon has been expecting them. An ancient prophecy names a hero, and the prophecy is written down in a book that talks. The locals treat the absurd as municipal business. Brokkenbroll commands the broken umbrellas. Obaday Fing cuts clothes from paper with a pin-cushion where his head should be. An empty milk carton called Curdle trots after the girls like a puppy. Giraffes hunt the streets. A cloud of smog has plans for the world.

China Miéville plays all of it straight, which is most of the comedy: nobody in UnLondon stops to explain the giraffes, and the jokes sit inside real menace rather than beside it. He illustrated the book himself, so the stray objects and half-people arrive drawn as well as described. It took the 2008 Locus Award for Best Young Adult Book.

Good for readers who want a portal fantasy with grime under it, and for anyone who reads a shop sign and wonders what the words get up to after closing time.