Read it! Un Lun Dun by China Mieville

from the Children's Literature review

"Twelve-year-old Deeba never imagined where she would end up the night she accompanied her best friend, Zanna, into the basement of the housing complex. But things had been getting stranger and stranger for her friend, with wild animals bowing to her, total strangers greeting her with reverence, and her name showing up in bridge graffiti. With the turn of a wheel Zanna and Deeba are transported to a fantastical world made up of all the things that are broken or discarded by the inhabitants of their former hometown, London; it is the shadow city, unLondon, where none of the rules of their previous lives apply. Animate milk cartons become pets, specially trained rubbish bins are soldiers, double-decker buses fly, words become creatures, and people dress in clothes made from the pages of books. Your best friends may not be fully human, like half-ghost-half-boy Hemi. Although Zanna is the Chosen One described in the prophecy book, the Smog has stolen her memory and it is left to Deeba to save unLondon from being taken over by evil forces. In his first young adult novel, Mieville creates a wildly imaginative setting and story on a par with Terry Pratchett's "Discworld" series. This hefty work has a serious message about pollution and the mindset of disposability, but it's also a good adventure—with intrepid young male and female protagonists—that will appeal to fantasy fans of both genders."