Alright, Scary Stories to Tell in the Dark is a 3 book series from Alvin Shwartz and none of these books are technically for adults..but they’re fabulously creepy nonetheless.
These were some of my favorite reads when I was a teenager, and the illustrations from the original books really lend to the creepiness (just see above)!
You can get all 3 books here on Amazon for $19.75
The Year of the Witching
If you like a decent dose of witches and magic, check out The Year of the Witching by Alexis Henderson.
The whole setting is very Salem-ish, and there are a few totally terrifying parts in this one!
You can get it here on Amazon for $14.99
50 Real American Ghost Stories
Get ready for hauntings and history with this book called 50 Real American Ghost Stories by MJ Wayland.