2001: A Space Odyssey is a classic science fiction novel as well as a classic movie. I have seen the movie several times, but didn't really consider reading the story until recently. I am so happy to have finally read it as the movie now makes a bit more sense.
The movie sticks pretty faithfully to the book so in this instance I think watching the movie is not that much of a loss relative to the original material. Clearly your imagination gets to do more work in the book, but having seen the movie first I ended up picturing a lot of what Stanley Kubrick created. Nevertheless, the ending of the movie has always been a topic of debate and confusion for me. The book, on the other hand, is basically clear as to what is going on. The movie follows this but without the explanation as to what it all means. I need to go back and watch the movie now armed with my foreknowledge, as I think the whole thing will be much more fulfilling.