Aaronovitch is back in form with this 10th instalment of the “Rivers of London” series. The series has been muddled, mediocre and meandering since Aaronivitch finished the “faceless man” part of it (the first seven books of the series, most of them very good), but this one flows well and is a fun book to read.

Peter Grant is in Scotland, with his whole extended family (Nightingale, his wife Beverly, his twins, his parents, his father’s jazz band and their manager, and his cousin Abigail) in a bit of a contrived mission to take a family holiday while looking into some strange cryptozoological incidents. There’s the familiar wry Peter Grant humour and Abigail sass (the narrative is split between the two), imaginative world-building (this time with mermaids and selkies) and a nice set of villains to catch.

The setting is interesting, the final battle is suitably epic, and I like Abigail’s new mermaid girlfriend. I think Aaronovitch is facing the issue where there are so many books in the series and so much history to it that it’s sometimes hard to follow who is who and what happened when, but he does a decent enough job of keeping the readers informed about the most crucial parts of the past. Abigail’s brother’s death lies heavy over this one, and Aaronovitch handles her grief with subtlety and heart.

If you’ve read the other books in the series you’re bound to love this one. It does still suffer from the “oh boy, big bad things are coming in the future, look at all these vague portents” issues that the past few books in the series have had. It’s clear that Aaronovitch want another villain in the calibre of the faceless-man but isn’t able to come up with one. It also has the usual overdose of architectural descriptions that you see with other books in the series.

Another peculiar thing about this book is the name. Stone and Sea or even Sea and Sky would have been better than Stone and Sky. You’l understand why once you read it.

A solid addition to a good urban fantasy series, well worth the read for series regulars – but if you’re just getting started, go to book one of the series, the excellent Rivers of London.