I did not expect a book on extra-terrestrial life to leave me thinking about the evolution of mankind.You won't find any alien action here, no war-of-the-worlds scenario. Instead, 2001 is a book that relies on the sheer strength of ideas - which is what I believe good science-fiction should be about. All those intriguing what-if and maybe questions that can challenge your beliefs and change your perspective.Maybe light is not the fastest medium there is. How do we know what lies buried on the moon? What if there are aliens out there who are so very alien that it's beyond out human faculties to even think of them as life forms?Okay, I'm freaking out a little.My point is, as fascinating as the book is, it's also utterly terrifying because almost everything about it seems plausible. Especially the part about Hal's malfunctioning. My blood nearly froze when that happened. Computers! Neural networks! Artificial Intelligence! Forget alien invasions, what if there's a Mutiny-of-the-Machines or something!.I did not fully understand the ending and I don't think I ever will. The implications of that are so immense that it's impossible to get your head around - pretty much like the universe itself.Or maybe I should say that the ending was too alien for my poor brain to make sense of.2001: A Space Odyssey is one of those books that have timeless appeal. No wonder this has been labelled as the best science-fiction book ever.