I wrote my dissertation on 2001... i've done too much analysis of Kubrick.
Rifa, I don't particularly think a lot of this is based on 'facts' the way you seem to be implying, he takes elements of the film and found extremely clever and effective ways to back them up with some facts about the movie. I don't think it's a leap from what most people do for most films, he just did it better, and is clearly well-researched and singular in what he brings to the table.
Still, I'd preferred him to comment specifically on other interpretations and so forth, since he seems to imply his interpretation means those are invalid (or at least unsatisfying), and my interpretation, and some of how the book ended, make a lot more objective sense than what he's arguing. (I.e. that going into the stargate is him literally passing through some form of inter-dimensional passageway outside the boundaries of space, time, and consciousness, and all the things he saw were merely planets, strange manifestations along the way, and very possibly other life forms. It may seem a bit simplistic and obvious, but his theory ignores a lot of these things, which made it a bit less effective than it may have been otherwise. Is that any clearer?