Because I may in fact be a masochist, if I read a book and it's been made into a movie I usually try to watch the film while the book is still fresh in my mind.
I recently watched John Carpenter's Vampires a week after reading Vampire$ by John Steakley. I'm not sure if Carpenter just wasn't right to make this film or if he didn't have the budget to make it very well. It's not very good.
The book is mediocre overall but there's a good story buried in there with a lot of time wasting side stuff, Carpenter throws out all of the compelling stuff and tells a more boring and predictable story that has very little of the suspense of the book.
My fellow Odeckers, what are your favorite or least favorite films made from books you've read?