Darkly Dreaming Dexter By Jeff Lindsay

Dexter Morgan appears to be the perfect gentleman. He leads a normal, quiet life working as a forensic officer for the Miami police. He has a nice, shy girlfriend and is liked by her young children.

But Dexter has a secret hobby. He's an accomplished serial killer. So far he's killed dozens of people and has never been caught, because he knows exactly how to dispose of the evidence. And there are those who would rather he wasn't caught at all, because Dexter is a serial killer with a difference. He only kills the city's bad guys. Then Dexter's well-organized life is thrown into chaos. Another serial killer is invading his territory - and he wants Dexter to come out and play...