Hey, I want to read something that makes me keep the light on at night. I want this story to make me feel like a hand is going to come over the side of my bed and rip me off of it. Do you have any good horror recommendations?

I've never actually found novels scary to be honest.  I was initially worried I would, but I didn't and now really enjoy horror novels.  However, I found that some horror novels were more enjoyable than others.  

Hell App - https://www.novelupdates.com/series/hell-app/
Probably the closest one of these novels has come to genuinely unsettling me.  

My House of Horrors - https://www.novelupdates.com/series/my-house-of-horrors/
Most enjoyable horror novel for it's novel ideas.  Lots of great horror storytelling.  Mainly ghost stories.  

Plague Doctor - https://www.novelupdates.com/series/plague-doctor/
Once again, top quality horror descriptions.  

Those are the ones that I loved.  There are lots of others, but I didn't really care for them. Some people like Thriller Paradise.  

One of the most terrifying stories I've ever read is the infamous web fiction Worm (not on Royal Road). It's fantastic but very long, and in my opinion the horror doesn't really start kicking in until around the one-third mark. Still, it filled me with the kind of terror you feel deep in your soul in parts. I'm pretty sure the act of reading it desensitised me to a few things as a writer. Would highly recommend.

I haven't seen a lot of horror on RR specifically, but I can recommend these two:

Keep Breathing is similar to a particular classic staple of the horror genre (no spoiling which) with a unique twist. It has fantastic characterisation, is very well written, and generally a good, solid read. I didn't find it particularly frightening, personally, but it's definitely a horror story and I can give it a strong recommendation.

My Delirium Alcazar is one of the weirdest genre-blurring stories you're likely to find on RR, with strong horror elements (including both psychological and body horror). It's fun and compelling with sympathetic and relatable characters, and heavy helpings of gamelit, surrealism and mystery thrown in to boot. Another very strong contender.

Perhaps Parasites and Magic by MimicFeline?

Palus Somni
No joke, it was so scary (esp with the recommended song) that I couldn't finish the first chapter, even with the compelling synopsis and excellent writing, it was just too much.

Katalepsis
Lots of body horror and eldrich abominations. Also maybe the single best web fiction I've ever read.

Stitched