For me it’s hard to say for sure, because my scariest book wasn’t meant as horror, but Communion by Whitley Streiber is definitely responsible for the most sleepless hours.
It’s tough to say - I tend to consider books that have stayed with me the ones that scared me the most. Off the top of my head:
- The Last Days of Jack Sparks by Jason Aarnop
- From A Buick 8 by King (though I’d say I found this one more existentially disturbing and unsettling)
- Drood by Dan Simmons
I think, looking at this not-at-all-exhaustive list, that the books I find scariest are the ones where you’re left with more questions than answers.
I just finished The Thing Between US by Gus Moreno. I’ve read a lot of horror and I’ve never jumped or turned my face away or slammed the book shut, but I did all of these things at different points in this book. Something about the way Gus Moreno describes things really freaked me out lol. It was a phenomenal book and I can’t stop thinking about it.
Penpal by Dathan Auerbach, was a book that really succeeded at scaring me personally. It managed to make me feel pretty vulnerable and it just filled me with dread the whole time I was reading it.
Probably isn’t really horror but I’ve never felt more uncomfortable than when I read House of Leaves. Just being alone in an apartment felt creepy while reading certain parts.