American Psycho by Brett Easton Ellis
Have read it several times and I find something new to disturb me every time. A challenging, thought provoking read that the film did little justice to.
Read it when it was first published. Very disturbing, about half way through I really wanted to give up but forced myself to finish it. Haven't watched the film as a result.
Think I'd take an Iain M Banks. Have read all his Ian Banks and love them and have really tried to get into the SciFi ones but lose the will to carry on about half way through. Would definitely keep me occupied.