[Guyver Spawn]

I seen many movies based on books and there is way too many to count. Most of my favorite movies of all time are based on books like The Godfather Part 1-2 (The third movie kinda sucks), A Clockwork Orange, Fear and Loathing in Las Vegas, Blade Runner, Full Metal Jacket, Die Hard, Pyscho, To Kill a Mockingbird, Hellraiser, Casino, The Shawshank Redemption and many others.

Some movies can be so different from the book and still be good. Like Naked Lunch from David Cronenberg or Starship Troopers from Paul Verhoeven. Both are fantastic movies based on good novels in my opinion. If you mean that you read a book before it was adapted into a movie, I have read books before they got adapted into a movie. I read The Snowman from Jo Nesbø before it adapted into a movie and the movie was a total letdown.