I believe that movies based on books are generally not as good, or lacking in some substance, so I always try to read the novel version first before watching the film. This was the case for 2001: A Space Odyssey.

What I didn't realize is that the movie and novel were created simultaneously. The novel is, in fact, a companion piece for the film, providing more context. So over the decades, I've watched as people struggled to understand the hidden meaning of this classic film. There are hundreds of articles written, or YouTube reviews posted, theorizing what the monolith is about, or what the big deal is with the giant space baby, etc. But if you read the book, it explains exactly what it is, right there!

If I had watched the movie on its own, I would've been totally lost. But reading the book first helped me understand the more "artsy" scenes, and the film actually makes sense from start to finish. It not only explains exactly what's happening in each scene, in simple non-metaphorical language, but you also see the inner dialogue of the main characters. Where there are quiet scenes throughout the movie (the film itself is about 90% quiet scenes), there's actual inner-monologues or exposition going on in the book.

So I'd highly recommend reading the book before you rewatch 2001: A Space Odyssey. You might get more enjoyment out of it.