I am going to say "The Time Traveler's Wife." I really loved the idea behind the story, but overall it was a disappointment.
I can't think of an underrated one right now.
"Eat, Pray, Love." I got through the first chapter and decided the author was self-absorbed, shallow, and wouldn't know hardship if it bit her on the a$$.
The Lord of the Rings books.... Just couldnt get into them, they might as well have been written in a different language!