I love watching movies based on books. And while there are many cases in which the cinematic vision lacks the depth and richness of its literary progenitor, there are many more that capture the spirit and intent of the written word in manner befitting our own imagination, or perhaps even improve upon it.
I’m sure you’ve got a list of your own, but for my money, you can’t do much better than Jaws and Forrest Gump (better than the books), The Shawshank Redemption and Jurassic Park (nearly as good as the movies), and the Harry Potter flicks (missing some ancillary details, but visually spot-on).