I already have Foundation. I can read it whenever I make the time. It's kind of cool to see a book translated to the screen... but if it doesn't really survive the translation? That's ok too! It can just be a movie with a ton of similarities to an existing story.

Blade Runner, The Shining, Starship Troopers, or hell, Adaptation. They all have varying relationships to the source material. None are especially faithful, but they're all still good movies.