I'd read this book before, but not since I was a kid, so I didn't remember it all that clearly. This "anniversary" edition of it also included an introduction by Clarke that was rather interesting, talking about the writing of the book and the making of the movie. However, Clarke mentioned in this introduction that he drew idea for the book from no fewer than four previously existing short stories of his – and, reading the story with that in mind, perhaps I was predisposed to consider problems of cohesiveness – but I really didn't feel, this time around, that the different parts of the story meshed well enough – the ideas and themes are quite different. First, is a story of an alien artifact which gives a boost to our primitive ancestors, enabling our evolutionary development. (possibly my favorite part of the book, and interesting in the moral ambiguity that progress is intertwined with the potential for violence.) Second, we have a very realistic look at what might happen, politically, in a near-future scenario when humanity is faced with the potentially significant discovery of an alien artifact. The third part (with HAL) is focused on individual human psychology and the potential for problems inherent in man's use of his own technology. Finally, the end of the book is an unusual and interesting "first contact" story (although, in my opinion, one that suffers from a both overblown and indeterminate ending.)
Sure, all of these issues reflect on each other and interconnect to some degree, creating a "big-picture" view of intelligence, evolution, and our possible place in the universe – mixed in with lots of (amazingly, not-too-outdated) speculations on space travel and our solar system. But I still found myself wishing for a more cohesive narrative..