I ended up listening to the audible version of this instead of reading it. This is definitely a psychological thriller. Sarah Baker (Olivia) is the sole survivor of the Watt Lake Killer and although you don't witness what happened to her, you certainly see the aftermath. It's not pretty.
The premise is that Sarah changed her name and is kind of in hiding having started her life over again after the killer died in prison. Except pretty early on, you discover maybe the killer isn't really dead. There are also a number of twists in turns that make you wonder if it's a copy cat, is the killer really still alive and you're trying to figure out the motive for stalking Sarah.
I will say that there is a scene late in the story that was reminiscent of the time I watched "The Shining" and the scene where Jack and his wife are on the stairs and she hits him with a bat. I was screaming "Hit Him Again Damn It HIT HIM AGAIN." It was pretty satisfying to be riding my bike yelling "Stab Him Again."