Disturbing Books ?

What would you name as the most disturbing books you've read..

For me it'd have to : Anything by Peter Sotos, De Sade, American Psycho by Bret Easton Ellis



 What about you ?

The Wasp Factory by Iain Banks. The bit where you find out exactly what turned Eric from an honour student into a psychopath who sets fire to dogs gave me nightmares for the next two nights. It also had me more or less breaking out in a cold sweat while reading it. Can't recommend this book enough.