I read The City & the City last year. I'm usually terribly disappointed by the Science Fiction/Fantasy sections at bookstores. It's usually a bunch of swords and unicorns books and then Warhammer and Star Wars, and that's about it. I saw Miéville's book in the new releases, and the jacket was encouraging, so I bought it on a whim. Excellent, excellent book.
I'm reading his newest book, Kraken. It's kind of a dark comedy. I'm about 25% through it so far, and it's great. However, I think that The City & the City best displays his writing prowess. It's a great example of noir fiction.