At first I thought this was my least favorite of the Harry Hole series. Then I realized just how brilliant Nesbo's character studies are. He builds such complex stories around characters that we don't even get to know much. Which leads to a point I need to make - this particular book in the series works best if you know some of the characters already. If you read it as part of the through-story it's brilliant, but might be confusing if you pick it up as a one off.
The book starts slowly, and the Redeemer is distant and hard to understand. It builds and gets terrifically interesting toward the end.
I'm going to continue picking these books up as they become available to me, but this book especially made me want to read them all in order.