I think I read the novelization first, too, but I can’t remember. I read it and watched the movie around about the same time, probably in the early 80s. I think the movie stands on its own just fine. Of course the novel adds more context and is a fuller story. That’s always the case.
I think a bigger difference was between the sequel novel and the sequel movie, 2010. That novel wasn’t an adaptation of the film screenplay, unlike 2001. The novel for 2010 came first, and then it was adapted into a screenplay. I thought the book was pretty good, but the movie wasn’t good at all. I also liked the third book, 2061. I never read the final one, 3001.
I’m sure it’s me - I find Kubrick films almost completely indecipherable and opaque. It’s not that the movie is bad per se - I’ve watched it multiple times, and really enjoy it - it’s just that I would never in a million years be able to figure it out on my own.
I re-watched 2010 recently, and it was definitely not as good as 2001, and not as good as I remembered it.