I've mentioned my admiration for author China Mieville before. I think he is the best writer alive today. I've yet to read a book of his that wasn't both well written and incredibly fascinating. It's been a while since his last book so I was pleasantly surprised when I heard about his latest novel, "The City & The City."
At its heart, "The City & The City" is a typical detective/murder mystery novel. The protagonist, Tyador Borlu, is a detective in the city of Beszel. Beszel is somewhere in Eastern Europe and isn't doing so great economically. Its sister city, Ul Qoma, however, is prospering. Tyador is tasked with investigating a murder of a young woman and soon finds himself embroiled in a crime that spans both cities.
As I said - fairly typical. However - there is one important aspect to the two cities. They aren't "sister cities" as in two close cities. Both cities actually occupy the same physical place. Yes - the same physical space. But wait - it gets better. Citizens of each city are trained - mentally - to simply ignore the other city. So you can be walking down one road and have the other city, physically, five feet from you. If a person you know is walking in the other city, you can't speak to them. You can't wave. You can't do anything that acknowledges their presence.
If that sounds weird... well it is. Mieville never actually comes out and states if something magical is going on here. Rather it is left to the reader to determine if there is some multi-dimensional hocus pocus are simply a mass form of self-delusion.
Mieville does an awesome job of combing both a great scifi/fantasy story along with an intricate mystery novel. I strongly recommend this novel, especially since it is also one of the more approachable Mieville novels. If you like this, definitely check out "King Rat", and when you are ready, "Perdido Street Station."