The Man Who Smiled, Henning Mankel, 2005

Kurt Wallander returns to the police force after a medical leave forced upon him after killing a suspect in self defense in the previous book.  Wallander nearly crumbles with depression, drinking and self loathing, but rejoins the force when a friend is murdered.  He discovers the man who smiles, Anders Hardenberg,  the owner of Farnholm Castle and a complete sociopath who had ordered the murders of two lawyers and an accountant and who was about to escape when Wallander intervenes in an exciting climax.  A good summer read.