Lavender Tower's Syndrome (or something along the lines) is simply amazing, if you ask me. I've read it only once, but it had an amazing effect on me; have been nervous for about three whole days afterwords. Though, last time I did read was about four years ago, so I might try giving it a go again. Usually, I'm not a fan of horror, but this story is definitely in my exception list. If you haven't tried it before, then you should probably consider!