Aaronovitch deftly balances urban fantasy with the police procedural. As for Grant, he's a wonderful blend of laconic copper and, methodically researching how magic works, full-on nerd.
This series is brilliant!
The Hanging Tree is definitely one of the best in the Grant/Aaronovitch pantheon. There again, so have most of the previous books in the series and the odds are the next one probably will be too.
Ben Aaronovitch is a master of metropolitan magical mayhem and the action is delightful. This is a tight thriller that is compelling and buckets of fun.