Midnight Riot by Ben Aaronovitch

This book, published in the UK as Rivers of London, features police constable Peter Grant, who sees a ghost on a murder investigation, just as he's about to get his first permanent assignment in the police force. Instead of being sent to a division of paper-pushers, he is apprenticed to Detective Chief Inspector Thomas Nightingale, who is apparently a wizard and responsible both for solving crimes with a supernatural element and serving as liaison between the police (and their interest in the Queen's Peace) and the various deities and supernatural entities (such as Father Thames and Mama Thames) who live in and around London. I thought the supernatural content was very well handled and balanced the murder mystery in a reasonable and entertaining fashion. I liked seeing the development of Grant and I loved the book's connections to London. I'm looking forward to the next entry in this series.