Best adaptation of a story (ever!) is, possibly, The Shawshank Redemption, by Frank Darabont. Based on a novella called Rita Hayworth and Shawshank Redemption by Stephen King. King is generally a better writer than people give him credit for, but the original story was just okay. It was simple, he apparently wrote it over a few days, and it was definitely not a horror / dark fantasy story, but just a prison drama. Darabont added to the original story, layering it with great scenes, changing it and turning it into something special. It's more literate than the original story, more meditative and it earns it's ending better than the novella.