I spent the entire evening after finishing this short novel walking around the house shaking my hands and going "ew, ew, ew". Now, you'll think that's because - as a novel set squarely in the horror genre - there's a ton of gore and sudden scary moments that make you jump out of your skin. Not in the slightest. It's creepy without having to resort to any of that.
Yes, there are plenty of spine-tingling chills and odd sudden unveilings. But the strength of the novel is in the depiction of its characters and their psychologies. You spend the entire novel specifically in the head of one of the characters - learning her thoughts, worries, and revelations. So, frankly, you learn her psychology and what she thinks and feels about the others' psychologies. It's a brilliant depiction of someone not completely... put together. And both her effect on the others around her, as well as the effect of the setting on her.
I strongly recommend this to anyone, especially in advance of the Netflix series coming out. It's worth reading Jackson's story beforehand. (I have some high hopes for this as a series because there is a lot they can delve into here, not just one particular character from the novel.)