If you want to read non-fiction, I suggest reading John E. Douglas, the guy who started the profile unit for the F.B.I.
As a former LEO I have read them all. - see also:Silence of the Lambs, Hannibal Lecter & the Red Dragon
You will be surprized, you will say"OMG, I know that guy!!!!".
"Sexual Homicide: Patterns and Motives."
"Mindhunter: Inside the FBI's Elite Serial Crime Unit."...read this one first
."Journey into Darkness."....and this one second.
"Obsession: The FBI's Legendary Profiler Probes the Psyches of Killers, Rapists and Stalkers and Their Victims and Tells How to Fight Back."
"The Anatomy of Motive: The FBI's Legendary Mindhunter Explores the Key to Understanding and Catching Violent Criminals."
"The Cases That Haunt Us."
I'm telling you, you read these profiles, you will know someone who fit them. Everyone has a Jeffery Dalmer intheir family. This is real life. Much more scary that fiction!!!!