Agree that A clockwork Orange - has to be up there on disturbing reads - yes disturbing but also I always thought how clever and thought provoking this book was
Also 1984
Another disturbing read of mine from a few years back is a book called The Amethysts" - Frank Delaney - A work of fiction but it leaves you with a haunting feeling that what you just read could actually be true
An off the wall and very recent read that I was haunted by is a book called Weightless - Sarah Bannan - totally chilling