The Hanging Tree

Ben Aaronovitch's sixth Peter Grant novel, The Hanging Tree, arrives with its hero as much a fixture of London as the river deities he shares the city with. Peter works for the Folly, the Metropolitan Police unit that handles cases involving magic, and he spends much of his week at the riverbank house of Beverley Brook, who is both his girlfriend and the goddess of a small south London river.

The case opens at a party in a very expensive block of flats, where a group of teenagers have been drinking and taking drugs and one of them, Christina Chorley, has died. Her link to Lady Tyburn, a river goddess with more influence than patience, turns an ordinary death into something Peter cannot walk away from, and the post-mortem points to a magical injury as well as an overdose.

Aaronovitch uses the investigation to walk his policeman through the parts of the city where money does the governing, and to bring back the history underneath his magic: a lost manuscript by Isaac Newton, the eighteenth-century criminal who stole it, and a great deal of money that would prefer the whole business to stay buried. The book keeps the series' habit of being funny on one page and genuinely uneasy on the next. The wealthy setting is new to the novels, and so is the suspicion that some of Peter's superiors would be happier if he stopped asking questions.