Just off the top of my head. There are more, certainly, but I try not to think of bad books unless I can help it.
The first two are kind of obvious; I didn't list Twilight because it was fairly original, in its day. It wasn't the book's fault that it spawned so many wannabes that are worse than Twilight could ever be. Even Stephanie Meyer said she is so over the Twilight hype, so I can forgive that series.
So many people loved the Lumatere Chronicles...I just don't get it. The world building was boring as hell. The main characters left me completely cold. The author tried to justify rape because *womp womp womp* the would-be-rapist was abused himself.
No. No. That excuse doesn't fly with me.