What are your recommendations for Psychological thriller/horror/torment themed books. (Mess with your mind type of thing or quite literally the MC’s mind.) YA is fine, though I’m looking for more mature content.

Before I go to Sleep by S. J. Watson was a really enjoyable read. I also love the movie Perfect Blue by Satoshi Kon and have the books (of the same name) by Yoshikazu Takeuchi on a read list already.