The City & the City

4.5* Basically, the core of this book is a really good murder mystery. What makes it great science fiction is the "City and the City" setting. Two. occasionally warring, Cities exist side by side, with some parts of each overlapping (i.e. "cross-hatched" streets and parks). They do business together, have a shared history and acknowledge the existence of each other. However, if a resident of one city hasn't legally travelled through the one checkpoint between the cities, they are forbidden to physically interact with the other City or inhabitants in any way. Residents are required to "unsee" anything from the other City or they risk "Breach" of protocols and an all powerful and seeing entity takes them away. This leads to some bizarre descriptions of traffic encounters on shared roads. The concept provides a refreshing twist to an otherwise straight forward investigation into a murder that takes place in one city with the body dumped in the other.