Darkly Dreaming Dexter, Jeff Lindsay

Darkly Dreaming Dexter.  A serial killer, who kills the bad people.  But he doesn’t just kill them; he confronts them, and makes them suffer.  And his way of killing is just as unique as he is.  It all started when he was just a boy, as we see in flashbacks throughout the book.  He would kill small animals such as squirrels, and once, his neighbor’s dog.  His adoptive father, Harry, worked for the police department at that time, and had found Dexter at the scene of a crime, and proceeded to adopting him. 

It wasn’t long before Harry realized what Dexter had gotten himself into, and what he was becoming.  The only thing he could do was intervene, and teach Dexter how to control himself.  Control himself enough so that he could fight off the urge to kill something, and only kill the people who deserved death (rapists, killers, etc).  Dexter fine-tuned his style from the beginning, carefully and dutifully working. 

Harry helped him, and helped him to find and know who the bad people were.  Dexter makes sure he has proof of the wrongdoings of the people he kills.  He works as a blood splatter analyst for the Miami police department, which also helps him during his moonlighting job.  However, when a string of murders display a resemblance to his own style of killing, he is both flattered and frightened- of himself and this mysterious murderer. 
This book series by Jeff Lindsay has inspired the Showtime series, Dexter.