I find movies much scarier than books for some reason. I was terrified for ages after seeing Scream, and a few years later I stupidly thought I was grown up enough to cope with Silence of the Lambs. But age made no difference - I was a wreck.

Anyway, in terms of scary books, I think I'd have to say The Historian by Elizabeth Kostova. The tension and build up of fear left me breathless as the characters followed the trail of the Dracula myth.

I am however reading Dracula right now, and I'm not very far in. So I might be back later to say it's scarier!