The City & the City by China Miéville

Ordinary detective story, but set in an extraordinary city. I won’t spoil any more of the plot, but what’s ingenious about this book is how the city sucks you in. You can feel the atmosphere of the two cities merging, yet trying their best not to acknowledge each other. There’s the secret police checking the rules and the mystery about the crime. I loved that the author doesn’t over-explain, allowing us to imagine the possible causes of such an arrangement. It was great, and I can still see the images in my head. It’s easily one of the top ten sci-fi books.