Need an “edge of my seat” book… thriller/suspense/horror…paranormal or crime. Totally new to the genre.

Within the past year, I really got into reading, and I read a lot of fantasy romance. But I got pregnant and reading became very difficult for me, since i have some attention difficulties and can't take my medication.

But I'm trying to get back into it, and so I'm looking for a thriller/suspense/creepy/"nail biter". I don't mind horror…i actually enjoy horror. I especially enjoy paranormal horror, if I had to choose. And I like crime thrillers. I like "something really creepy/mysterious is going on here (in this house, with this person, etc.) and we need to figure it out quickly" whether it's realistic or paranormal…don't care. I'm totally new to this book genre. But I love movies like that. I did start Lights Out a few months ago, but haven't finished it.

But i really want an "on the edge of my seat" type of book…..since it's more difficult to concentrate when I'm pregnant. Preferably under 500 pages.

Thank you