...the book you got the least "worth" from for the time you spent reading it.
What made you read it? Was it assigned in class? Did someone else rave about it? Was it based on a movie (or the reverse)?
I had to read Don Quixote in Spanish class. That, or In Search of Excellence, which was assigned in a college business management class, are tops on my list.
This is kind of the Dark Side of Stinkypantz's thread about favorite books.