Scariest Book

I believe I have only read three Stephen King Books, Carrie, Fire Starter (possibly the only novel to have a scene set in Albany Airport (NY)), and Salem’s LotSalem’s Lot was the scariest book, vampire, paranormal or other.  I am not alone; looking at reviews for the book on Amazon I found one by Christopher Blair of Dallas, TX he says:

    The metric by which one must measure any good horror story is the
    degree to which it scared you. Well, let me tell you, “Salem’s Lot” 
    scared the ever-loving &#$*@! out of me–AS I read it!

I think I was 16 at the time I read this, not a very sophisticated 16.  I would not open my windows for a year, and put garlic between the window and the screen.  My mother already thought I was insane so nothing lost there.  I don’t think I read any fantasy until  I started taking Arthurian legend, Fantasy and Celtic lit classes to fulfill my minor. No book has ever come close to the visceral fear engendered in those pages. I think it was the hopeless helplessness of the residents of the town the Vamps take over that got me.  It was akin to those dreams in which you are trying to run from a danger and you can’t. Anne Rice’s vampires are no where near as scary as Mr. King’s.  Brrrrr.
What is the scariest book you ever read?