Most Helpful Guy
The Girl with the Dragon Tattoo is a FANTASTIC crime/mystery/thriller trilogy. You've probably heard of it. The movies are good too, although the Swedish release was better than the English-language remake.
Another famous crime/mystery/thriller is Thomas Harris' classic Red Dragon, followed by it's sequels Silence of the Lambs and Hannibal. You've probably also heard of these. These books were made into movies that were even more fantastic than the books. They contain a lot of interesting concepts from psychology
BE WARNED both of these books and their movies contain some FUCKED UP SHIT. Rape scenes, cannibals, psycho serial killers that disembowel their victims. They are the type of crime fiction that REALLY disturbs you with how dark they are.
Most Helpful Girl
penpal which is pretty much a really long creepypasta but it's extremely well written and you can read it online for free so there's that lol