A Darkness More Than Night — Michael Connelly

It was a case some cops could live with: the torture killing of a man who spread horrors of his own. Yet one investigator believes the unknown assailant will strike again, and she persuades former criminal profiler Terry McCaleb to leave his quiet life to help her out. In a horrific morass of crime scene details, McCaleb deciphers a message and finds a suspect: a Los Angeles detective named Harry Bosch who has spent too many years looking at too much darkness. But while Bosch may have had a good reason to murder a man in a West Hollywood apartment, he has an even better one for staying alive - and for finding a suspect of his own.