Stone and Sky by Ben Aaronovitch

The tenth book in the Rivers of London series finds our heroes a long way from home - there have been reports of a giant cat in the Scottish highlands, possibly supernatural in origin, so what better excuse for all of the principal cast to travel to Aberdeen for a working holiday. Inspector Nightingale and apprentice Abigail prepare for a big game hunt whilst Peter's unique skills are called upon when the local police find the naked body of a man on the sea front. How did he get there and why does the autopsy report say that he has gills? Add in a strange girl armed with a spear, demonic seagulls, a missing scientist and shady tycoons linked to the North Sea oil industry and you have an intriguing mystery.

The various strands of the story combine nicely, and the audiobook is narrated in chapters alternating between the viewpoints of Peter (voiced by series regular Kobna Holdbrook-Smith) and Abigail (Shvorne Marks). Both narrators do a good job of the various different Scottish accents that appear in the story and this approach gives the series a fresh twist. I particularly enjoyed the appearances of Abigail's fox companions who seem to think that they are secret agents on assignment. 

I enjoyed it, even though the ending seemed a little rushed. I had the feeling that a couple of scenes had been dropped somewhere in the editing process making the denouement a bit confusing. I also got the impression that the author had moved almost all of the main characters up to Scotland at the start of the story, and then didn't really know what to do with most of them.