The monolith really works as a Visial metaphor for the Cinema screen. Just as the movie starts as we are staring at the monolith ready to go on a literal space Odyssey.

It's a shame so many re-releases "fixed" the faux screen jump when Bowman nearly touched the edge, and instead shattered the glass. It really is brilliant, a movie within a movie.

All through the film there are so many rotating monoliths it's incredible that we never get the hint that the upright position of the monolith as it is presented is incorrect.

Even the actual end leaves us starting at the monolith, with the profound music.

If you dig for interviews you'll see that Kubrick always said that the simple surface story is the simple alien device that transforms man.