I've already tried, and failed, to write a synopsis for this wonderfully bizarre book so I thought I'd include the quite well done blurb from the back cover of the book:
"What is Un Lun Dun? It is London through the looking glass, an urban Wonderland of strange delights where words are alive, a jungle lurks behind the door of an ordinary house, carnivorous giraffes stalk the streets, and a dark cloud dreams of burning the world. It is a city awaiting its hero, whose coming was prophesied long ago, set down for all time in the pages of a talking book.
"When twelve-year-old Zanna and her friend Deeba find a secret entrance leading out of London and into this strange city, it seems that the ancient prophecy is coming true at last. But then things begin to go shockingly wrong."
- blurb from book cover
Mieville turns upside down the rather cliche storyline of prophecies and heroic quests. Just about the time I was saying to myself, "Not another book with a several hundred page quest," the author caught me out and turned all of my expectations on their metaphoric heads. And that bit in the above blurb making a wee comparison to Alice in Wonderland? It is true. The story is that strange. In fact, don't the following illustrations by Mieville himself make you think of Wonderland?
Mieville has a grand time playing with words throughout the book and even includes a fantastic little "treatise" on the meaning of words. You will find that in the chapter with Mr. Speaker, of course.
If you like urban fantasy with a fun twist, you should thoroughly enjoy Un Lun Dun!