Peter Grant is a probationary constable with the London police. He wants to be a detective one day, but his superiors see his future to lie in the realms of data entry - desk support for the coppers out on the street so they don't drown in paper work. Then, one night as he's standing guard on a crime scene, a witness comes forward with an account of the murder - the only problem is that Grant can't do anything with the information, because his witness is a ghost.
Thus begins Rivers of London, the first volume of Ben Aaronovitch's urban fantasy detective series. As is the common conceit in this subgenre, there is a secret branch of the police tasked with the investigation of crimes with a supernatural aspect - though the wrinkle here is that, in the belief that science is making the notion of having sorcerers on the police force obsolete, there's only one active member of the supernatural investigations unit, Chief Inspector Thomas Nightingale, and he's not welcomed by other senior investigators when he shows up.
But after he sees the ghost witness, Grant is approached by Nightingale and invited to become his apprentice, and the first new member of the supernatural investigations unit in a vey long time. Rivers of London is the story of Grant's first experiences with the magical and mystical side of police work, and his early days as an apprentice sorcerer.
As using magic seems to do things like short out modern technology, Grant is forced to turn to a colleague and friend, Constable Lesley May, for access to regular sources of information such as surveillance footage and police databases. May seems to take Grant's entry into the world of sorcery in stride, so much so that she's more or less acknowledged by her governor (Britcop speak for senior officer) as a liaison to the sorcery unit.
One thing I liked very much about Rivers of London that I don't always find in detective stories, fantasy or mundane, set in London is an acknowledgement of the multiracial makeup of the city. Grant himself is of mixed racial background, and in a marvellous comment on the ways that generations of immigration from former colonial holdings have changed the city, the current physical vessel of the spirit of Mother Thames is a black woman who understands her metaphysical circumstances within the framework of West African religious tradition.
I also enjoyed the way that Aaronovitch makes use of the history of London, from its early days as a Roman camp to the founding of the Bow Street Runners, weaving small threads from the enormous tapestry that is the two-thousand year story of London into the narrative.
In fact, I enjoyed Rivers of London and am rather intrigued to see where the next volume takes Peter Grant, and us.