These are the books don't play as well with others, or will definitely, at least, creep you out. It takes a lot for a book to unsettle, scary, or creep me out. It takes even more for a book to disgust me in some ways.
House of Leaves by Mark Z. Danielewski (standalone)
I read this book over the course of a few months (February to April). It's a hard book to get to - the design is strange, it's slow and the tension builds very slowly and it's confusing. This book doesn't take you into account, it just goes with it. It's very visual, at points the words mimic what they're saying is happening.
It honestly creeped me out, had my heart pounding. It made me claustrophobic at points. It's differently not for everyone - it's a huge, strange, confusing, creepy book. But it's very, very good if you think it's for you, I highly recommend it.
It by Stephen King (standalone)
This book is long, alright? And it's strange and fucked up and I completely adore it. I'm completely biased on this book, first off. I first read this book at the same age the kids are, 11, and I read it over and over. I've reread this book possibly more then a Harry Potter book.
It's about a group of seven people - going between when they were 11 and then them over 20 years later, having forgotten about their childhood. It's about the characters, at least in my opinion, more then anything. About these seven kids and them being friends and together against all odd and - and also about a lot of fucked up, creepy things. It's why I liked this book so much at first, it's scary, creepy, and a bit gross at points. I'd highly, highly recommend this one.
Also - the movie that was made for this was made in 1990 and is 4 hours long and is actually pretty good. They're planning remakes, but that one was only missing a few things I wanted (and the affects weren't the best, but only laughable at one scene towards the end, the end is where I have most of my problems with it).
Duma Key by Stephen King (standalone)
I've reread this on a fair number of times, I also think I first read this when I was 11 (listen, some kids read Nancy Drew or whatever, I went from Harry Potter to Stephen King and I liked that). This was written after King's own accident that he had and so it's about a guy who pretty much gets crushed by a machine on a job site, much more extreme then King's accident.
And him moving to Florida for a change of pace and starting to paint - and everything that happens there. Learning about where he is, the history, and that maybe he should be more careful about what he's painting. It made my skin crawl at points, it's creepy and strange but also lovely and fantastic. The characters will dig into your heart and the story will intrigue you. Definitely up there for a favorite King book and not one that's talked about much. Also, not as scary as I think others are, or as long - if you're looking for a place to start with his full length stuff.
The Storm of the Century: An Original Screenplay by Stephen King
The movie is fine, even good, but I love, love this screenplay. I'd totally forgotten about it, but there was a time when I sang it's praises. It's creepy, taking place on an island off the coast of Maine during the storm of the century, a huge storm that causes all kinds of problem while something else is going on. It's strange and creepy and really good.
Dreamcatch by Stephen King (standalone)
This was, also, an early read for me. I think I saw part of the movie first (also good and I have a whole movies post coming up), but it made me interested so I read the book. And holy crap - I loved it. I loved it a lot. With King's books - it's always about the characters, for me at least and I think it just is, there's a lot happening and that's also very important but all of his characters - you get attached to them so completely. These four, five, I love. And the little It easter egg.
Bag of Bones by Stephen King (standalone)
I promise this is my last King recommendation (for now). This I also read when I was 11 (I read a lot at that age. I had a deal with my math teacher if I got 95+ on everything, I could read in class. Where did those math talents go, though?). Anyway - this is definitely scarier then the other two, in my opinion, there's no build up to the creepy, scary stuff. It's there quickly and it stays there.
There was a two episode mini series done in 2011 of it - that is no where close to the book, but I thought it was alright, interesting at least, if you want to watch it after the book. (Don't want it first, it's not worth it).
The Preacher, Vol 1 by Garth Ennis, Steve Dillion (graphic novel series)
I've only read Volume 1 so far - but it was gorey, a tad ridiculous, strange, creepy - and a freaking ton of fun. The art work is fantastic, but it does get very bloody and a bit gross at parts, so I'd steer clear if you're not alright with that.
The Expanse Series by James S.A. Corey
This is primarily space opera - but it's also horror. This is the first space book that made me feel claustrophobic and panicy from them just being in a spaceship, at one point. There are also vomit zombies, as they are so lovingly termed (I don't even remember if that's an actual term used, but one of the authors used it, I think, and I like it). I've only read book one and two in this series, but I've loved them both - they were fast paced, character-centric, with definite horror elements. And this is being made into a series that's going to be on SyFy, which I'm super excited for.
World War Z by Max Brooks
I didn't put this on my initial list, because I forgot it was horror, as I do apparently. This book was fantastic and incredible. I don't want to give you any real information besides it's written like interviews and it's incredible and don't watch the movie (the movie is based on the book, technically, but from what I saw of it before I rage quit it had nothing to do with the book besides zombies). If you like audiobooks, I'd highly recommend getting the full version of this - it's awesome to hear the different voices and completely incredible.
Something from the Nightside (Nightside #1) by Simon R. Green
This isn't in the same vein as the others, I only gave it 3/5 stars, but I still really liked it and it was gritty and strange and very dark. I'm going to continue on with the series, eventually, but I do recommend it. It's like pulp horror, I guess, is a good way to put it. It isn't fantastic, but it's a ton of fun and definitely creepy and weird/strange.
Making this post has made me realize how few horror books I've actual read. I felt like I'd read a lot, but apparently not. I mean I've read quite a few and some other people consider horror, that I havne't put on here, and this isn't all of my recommendations (I have more King up my sleeve, always).
Dolores Claiborne by Stephen King (highly recommended)
The Long Walk by Stephen King
Everything's Eventual: 14 Dark Tales by Stephen King (these last two I haven't read in a long time, but I remember really enjoying both of them).
Pet Sematary by Stephen King (don't read if you don't want to continually eye your pets with suspicious afterwards)
Books I guess are kind of horror (that others have classed as it, but I wouldn't):
Sookie Stackhouse series by Charlaine Harris (after rereading book one - it's an alright series, definitely gorey and has a lot of sex, for more mature audiences)
Anita Blake Series by Laurell K. Hamilton (I can see the horror elements in some of them, especially as Anita gets more terrifying, Obsidian Butterfly was the last I read and probably creeped me out the most, I haven't read on because I know it becomes all sex for a while).
In Death series by J.D. Robb (this is a series following Detective Eve Dallas and is more character centric, with all that as the backdrop, but some of the cases are creepy, weird, sad, horrifying, and/or gross, so I guess it does probably fall under it. Imitation in Death was probably the closest to horror, at least that I remember. Even so - much more character centric, still highly recommended).
The Time Machine by H.G. Wells
I only recommended books I've read, but there's a ton I haven't (a few obvious classics are missing), but if you're curious.... I made a horror shelf on Goodreads (that really horror/thriller), but if you want to know what I want to read that horror, check if out. And if you have any recommendations of your own, even if they're already on my TBR, let me know and it might make me bump it up the list - I'm always for talking about books!