Don Quixote and The Diary of Anne Franks.
I may get it in the neck from certain people, but the diary was totally boring. If it wasn't for the subject matter, and the horrific events it portrayed, I doubt it would have been published.
As for Don Quixote, the book would have been a lot more interesting if he'd fallen off his donkey, got concussion and been confined to bed - where he subsequently spent his last few remaining days discerning patterns from the wallpaper, or flames from the fire.