Double Dexter. Jeff Lindsay. 2012.

Dexter is displeased. Like any self-respecting, totally decent, soundly homicidal guy, Dexter Morgan takes great pride in his work and is careful to remain anonymous. So he is, naturally, upset to discover that someone has identified him and—worst of all—is now turning his own methods against him. The situation soon becomes more complicated when a brutal cop-killer begins targeting Miami’s police detectives—leaving behind bodies that are battered beyond recognition—and stoking the department’s worst fears. As his colleagues grow more paranoid of the psychotic killer in their midst, Dexter’s position is increasingly perilous. He is running out of time to track down this copycat and deliver his usual special justice, before his dark hobby is revealed to the world.