I'm not sure I agree with this.
For starters, the film 2001: A Space Odyssey was based on a short story by Arthur C. Clarke called "The Sentinel." Clarke wrote the novel at the same time the movie was being made, and it was actually released after the movie, so it's essentially an adaptation of the film and by no means essential to appreciating or understanding the film.
What's more, Kubrick has a track record for taking the material he is bringing to the screen and adding to it or taking it in new directions not expressed in the written work -- see The Shining, for example, which diverges from Stephen King's book wildly.
Kubrick's film should be enjoyed as a film. All these comments saying you need to read the book to understand it just sound like people who couldn't understand the movie and feel guilty about it, so they went and got the book from the library. Don't feel guilty. The film is designed to be a bit inscrutable and to inspire thought and debate.