Anything by Dan Brown but especially The Da Vinci Code
I picked this one up "to see what all the fuss was about", and put it down after about 50 pages.
Enders Game
I will possibly upset a lot of people with this one but the twist in the end was obvious really early and the main character was terrible. Really shallow writing. I was honestly shocked when I realised just how popular it was.
There is so much better SF out there I still don't understand it.