I've no idea how I missed this one! But Terry Pratchett's The Colour of Magic was made into a movie back in 2008! I recently started reading the book and came across it quite by accident while searching for an image of the book cover. I just started watching it and it's pretty good so far. And Sean Astin and Tim Curry are in it no less!
It you're not familiar with the series, I won't give away much. But if you are a fan of Hitchhiker's Guide To The Galaxy you'll like this story too!