These days, it's hard to find a movie based on a completely original idea. More than likely, you're going to find movies that have been adapted from pre-existing stories, with books as the most popular medium. That's not necessarily a bad thing: books being made into movies has been a staple of the cinema scene since forever. Many movie classics were based on books, and in some cases, the movie ends up being better than the book, or at least better well-known: I'm looking at you The Godfather and The Shawshank Redemption. Still, sometimes it's better to just let the books remain as books. The movie adaptation formula doesn't always work, and more often than not, we get adaptations that pale in comparison to the original written works. And I'm not just talking about leaving a movie thinking: "That was good, but the book was better." I'm talking about movies where, having seen them, you have to re-read the book as quickly as possible just to assure yourself that the original story was actually good. So movie studios, listen up: just because you have the opportunity to turn a book into a movie doesn't mean you always should. Sometimes, that unforgettable story that people loved and admired can't be replicated on the silver screen. Sometimes, a two-hour running time isn't enough to squeeze everything into a coherent narrative. Sometimes, altering the book's story to make it more appealing to a movie audience doesn't actually make it more appealing. Don't believe me? Take a look at the 10 movie adaptations gathered here - all terrible compared to the books that they were based upon...