An interesting outing from a new-to-me author, but I can't say I cared much for any of the characters, less for the disillusioned-communist backstory, and it wasn't much of a whodunnit - we know almost from the start
who dunnit, and the list of possible who-was-dids is small.
So, I'd try another book by Indridason, but won't be pushing him to the top of my to-read list.