To give you some background on what I'm into here are the books in the genre I read and enjoyed so far:
First and foremost on this list has to go to the series "John dies at the end" truly peak one of my all time favorites
coming in at a close second is "a short stay in hell" by Steven L Peck the only book I've read that really made me afraid of infinity or just really big numbers
Next on this list is Coraline while technically a YA book it gave me the definitive creeps it deserves its spot in the horror genre
Next this is a more recently published book but I have to say it was a whole new experience for me the plot was just so unique "there is no antimemetics division" by qntm was just really special I enjoyed it immensely
Next up we have Fabius Bile as part of the Warhammer universe you might argue everything to do with Warhammer is technically horror but this one definitely takes the cake and features one of my favorite characters
Next up I never hear anyone talk about this book but its incredibly imaginative yet dark it's called Abarat by Clive Barker starts off like a kids book ends in a very twisted dark way
Honorouble mention would have to be Lovecraft my favorite is the necronomicon
Last one I'll mention cause I don't want this to be too long is Dante's Inferno the divine comedy I don't read that many of the classics hardly any to be honest but I really enjoyed this one it has great re-read ability one of my favorites for sure.
Last on the list
by Atticus914