I really enjoyed this - a great idea for a novel (something out there turns you mad if you look at it) where the characters are trapped together inside a house, and every time someone else knocks on the door asking to be let in, you don't know who it's going to be. Malerman handles the tension incredibly well; slipping between three time periods to keep me turning the pages.
It's not literary, and doesn't try to be (but I do generally prefer my books with more crafted sentences). There were a few times where the dialogue (or dialogue as exposition) clunked, but it didn't spoil the book for me.
I wasn't terribly scared; it only scored 3/5 on the scary scale for me, but I was anxious and tense, and thoroughly enjoyed those feelings.