By China Miéville
There has been a brutal murder, and it is up to the suitably jaded but dogged Inspector Tyador Borlú of the Extreme Crime Squad to investigate. But this case is different than most in the city of Besźel, as the crime was possibly somewhere else both close by and impossibly far away - Ul Qoma.
Besźel and Ul Qoma are two cities that occupy the same geographical location, literally intermingled in all senses except by the behaviour of their citizens. Some blocks and streets are totally in Besźel, some totally in Ul Quma, but many are "crosshatched" - belonging to both cities although under different names.
The inhabitants of each city are conditioned from birth to never interact with anything in the other city, carefully averting their gaze and ignoring ("unseeing") as much as possible the sights and sounds coming from the foreigners around them. Driving on crosshatched roads is a pretty hairy experience. Strict rules penalise anyone breaching the imaginary boundary between the two locations. In fact the crime of "breaching" is much worse than the murder Borlú is trying to solve - transgressors are quickly dragged off by mysterious figures, never to be seen again.
Solving this crime will take Borlú into the seedy underbelly of Besźel, where gangs nationalists opposed to even the slight contact between the cities struggle violently with unificationists who want to end the separation. But could the answer lie in Ul Qoma, a city with an underbelly of its own?
China Miéville showed a Dickens-esque ear for language in his excellent fantasy novels, and here he puts it to great use writing what is a great whodunit police procedural set in a slightly strange place. The City and The City is a genre piece, but the genre is gritty crime novel rather than fantasy and the book follows all the usual rules and doesn't cheat by introducing new rules at the last minute although, of course, misleading clues abound. There is very few good whodunit/fantasy crossovers and this is by far the best I have come across.
Reading around the Internet, I see that people have taken the split (or joined, depending on how you look at it) city as a metaphor for all sorts of things. Does unseeing represent class distinctions, racial separation, a method or Orwellian control, or something totally different? Miéville isn't going to provide the answers in the book - the best allegories are those where no one has any idea what you are getting at, or even if you are getting at anything at all.