I like slasher/ demented stories from the mind of Laymon. His mind was damn twisted and it shows. But I love the way he manipulates the relationships of characters and the way he describes gore, always been a favourite.
Like RIP though, I also adore true crime novels. It's both intriguing (and of course) creepy how the true human mind can be so horrific and disturbing. 
P.S. My biggest true crime addiction is Jack the Ripper, I have read so many books on this potent time in history I cannot name how many LOL. I love mysteries that just cannot be solved, no matter how we try 