I Am Not a Serial Killer (John Cleaver, 1)

John works in his family's mortuary and has an obsession with serial killers. He wants to be a good person but fears he is a sociopath, and for years he has suppressed his dark side through a strict system of rules designed to mimic "normal" behavior.

Then a demon begins stalking his small town and killing people one by one, and John is forced to give in to his darker nature in order to save them. As he struggles to understand the demon and find a way to kill it, his own mind begins to unravel until he fears he may never regain control. Faced with the reality that he is, perhaps, more monstrous than the monster he is fighting, John must make a final stand against the horrors of both the demon and himself.