Black Skies by Arnaldur Indridason

From the villas of Reykjavík's banking elite to a sordid basement flat, Black Skies is a superb story of greed, pride, and murder from one of Europe's most successful crime writers.
Arnaldur Indridason, whom The Sunday Times calls "one of the most brilliant crime writers of his generation," has thrilled readers around the world with his series set in Reykjavik. In Black Skies, Indridason further cements his position as one of today's top international crime writers.
A man is making a crude leather mask with an iron spike fixed in the middle of the forehead. It is a "death mask," once used by Icelandic farmers to slaughter calves, and he has revenge in mind. Meanwhile, a school reunion has left Inspector Erlendur's colleague Sigurdur Óli unhappy with life in the police force. While Iceland is enjoying an economic boom, Óli's relationship is on the rocks and soon even his position in the department is compromised. When a favor to a friend goes wrong and a woman dies before his eyes, Oli has a murder investigation on his hands.
"A sophisticated and complex thriller."
-Kirkus