Book: Rivers of London
Author: Ben Aaronovitch
Ben Aaronovitch has written for television in the past, including the original series of Doctor Who (Remembrance of the Daleks, Battlefield) and novels related to the series. This book is the first in a new series of urban fantasy books, also called Rivers of London, that are set in London.
Peter Grant is a probationary constable in London's Metropolitan Police Service, the police force which has the responsibility for policing Greater London - with the exception of the City of London, or "square mile" - a police force with enough manpower and armament to invade a small country.
This transfer seems to the CPU seems very likely, when, along with WPC May, he is assigned to guard a murder scene in the middle of the night. Whilst guarding the scene, he takes a witness statement regarding the murder from someone who turns out to be a ghost. Not your everyday witness statement that.
Attempting to find the ghost again, he comes to the attention of Detective Chief Inspector Thomas Nightingale, who has him assigned to Nightingale's branch of the MPS. Which consists of Nightingale, a rather unusual servant called Molly who doesn't seem entirely human, and now Detective Constable Peter Grant. DCI Nightingale informs Grant that a lot of the creatures and beings from folklore and mythology aren't as imaginary as they are portrayed. Or, in some cases, as imaginary as might be preferred. They operate out of a large, and nowadays deserted except for the three of them, building known as the Folly.
DCI Nightingale is a wizard, and his job for the police is to enforce the law on the more unusual and super-natural law breakers, of which it appears the assailant in the murder Grant was originally guarding the crime scene is. A series of seemingly random yet related crimes and murders across London have Grant introduced to the spirits of the rivers of London, as well as trying to study to become a wizard in his own right, all the while trying to get a lead on the vengeful spirit who is making the residents perform acts of violence against their fellows.
There is a fair amount of humour in the book, although it isn't humorous itself, rather the humour is built into DC Grant's observances of the various happenings. This is a detective story with a number of twists - the detectives have unusual powers and the criminal they're in pursuit of doesn't always inhabit the same body.
If you have read and liked the Dresden Files series by Jim Butcher, you'll probably like Rivers of London too.