What is the worst cinematic adaptation of a book?

We’ve all heard it before. Disappointed bibliophiles wandering out of a theater saying “The book was better…”

So sure, the book was pretty much always better. What we’re looking for here is the worst movie adaptation of all time. Didn’t have to be a great book (or even an awful movie for that matter), I just want the biggest gulf between how good the book was and how bad the movie was.