I've previously reviewed two books in Jo Nesbo's mystery series about Harry Hole here. I missed one book in the series after those two but just read The Redeemer, book four. The series just keeps getting better.
The Redeemer has a complex plot which keeps you turning the page as fast as you can read. Surprises keep coming; what's more, they're all pretty credible, since the characters' motivations have been quite well laid out beforehand. And when you think the surprises are finishes, along comes the one final truly mind-blowing surprise, which you are completely unprepared for.
The book explores yet again the situations of immigrants to Norway, this time immigrants from the former Yugoslav republic, and continues the ongoing exploration of corruption in the police force.
The Harry Hole character is very interesting. He's an alcoholic, he's a loner who has many relationships with women, he's disdainful of authority, he's sympathetic with the underdog, he's loyal but undemonstrative. He's determined to see justice done, even if not the formal Justice of the system.
Most interestingly, Hole is that rare human who can formulate a solution and yet remain open-minded enough to abandon the hypothesis when new evidence comes to light. Most people tend to stick to their first credible solution and then interpret the evidence to support that hypothesis from then on. You can observe this phenomenon in medicine where practitioners fall in love with their first diagnosis and subsequent data that assails that diagnosis is ignored. You can see it in business where people leap on the first viable solution rather than searching for the optimum one (read Roger Martin's work on this kind of pitfall). This kind of confirmation bias affects us all. But Hole is a detective who keeps processing clues after the 'solution' appears to be all locked up. Anomalies nag him, until they point in yet a different direction for the solution. It's an interesting character.