What’s the scariest book you’ve ever read?

I don’t tend to read  books that I think might be scary, as I think that they might be scary, and don’t want to read them in the first place.

When I was a child I found the book The Children of Green Knowe quite scary. The only Stephen King novel that I have read was Carrie, which was quite scary, although I had to stop reading Pet Cemetary as it was scaring the shit out of me.