1. Out of the Night #5 - which there isn't a cover for. It's one of those horror comic books from the 1950s.
2. Uncle Silas and A Glass Darkly - if you haven't read Le Fanu, you haven't read horror, and Uncle Silas is just that hook filled book.
3. 2666 - not strictly horror, but I was reading this book and when I came home late, I was frightened when walking the half block from the trolley stop to my house, so that has to count for something.
4. M R James - he makes jars scary.
5. Watership Down - not horror I know, but you get to that chapter about the black rabbit of death and the rabbit poker game when you're like seven, and you sleep with the lights on.
I may I also suggest 50 Shades of Grey which I don't like but it is truly frightening when you read this and wonder why so many people think it is good.