Stone and Sky (Rivers of London, #10) by Ben Aaronovitch

'This isn't London. The rules are different up here, and so are the allegiances.'

Detective Sergeant Peter Grant takes a much-needed holiday up in Scotland. And he'll need one when this is over...

If more's the merrier, then it's ecstatic as his partner Beverley, their young twins, his mum, dad, his dad's band and their dodgy manager all tag along. Even his boss, DCI Thomas Nightingale, takes in the coastal airs as he trains Peter's cousin Abigail in the arcane arts.

And they'll need them too, because Scotland's Granite City has more than its fair share of history and mystery, myth ... and murder.

When a body is found in a bus stop, fresh from the sea, the case smells fishy from the off.

Something may be stirring beyond the bay - but there's something far stranger in the sky...