First and foremost, I'll say I have not seen the movie. Only thing I knew going in was that the movie is a classic, and HAL turns evil. Needless to say, I had some surprises waiting for me.
What I enjoy about good science fiction is how the author can make the most fantastical events seem not only possible, but downright plausible. Compared to say, Star Wars, space travel in 2001 is difficult, slow, and impossible when looking at moving beyond the reach of our own sun. This all is shaken when an alien artifact is found on the moon, and is indisputably declared 3 million years old.
Oh, did I mention 3 million years old? Let me back up a moment. The book starts 3 million years ago. Forget the 10,000 years Asimov spans with his Foundation series; here we've got 3 million crossed in the span of a few opening chapters. It's an enjoyable bit, watching as aliens effectively guide the evolution of man, alerting them to the ideas of tools, and therefore inescapably, warfare.
Of course, here I am expecting some sorta space shuttle with a killer AI program, and instead I get cavemen and alien objects on the moon. Loved every second of it, too. I want good science fiction to give me ideas, things to ponder over or wonder about the implications. An alien object waiting for us on the moon, which gives out a signal when dug up? What does it mean? Is it a warning? A guide? Will spaceships arrive to Earth, and if so, in how long? Will they be friendly? Ready for war? Or do the aliens even still exist 3 million years later? What sort of empire could endure for that long, what with us silly humans ready to nuke ourselves into dust within a few years of actually launching into space?
Anyway, the HAL segments actually intrigued me the least. Maybe by now I've just read and seen too many rogue AI stories to be surprised by this one. From what little I know, this segment is much longer in the movie, and given the variety of topics covered in the book, this is probably the strongest and wisest area to expand.
It's after HAL is disconnected that things get really interesting. I'm sure there are plenty who don't like the ending, but I LOVED it.
Gimme big. Gimme epic. Gimme a reprogrammed man with god-like powers arriving at Earth, blowing up the moon, and floating amid the debris trying to decide just what to do with his new home. That image is awesome, the potential stories following incredible.
Was the book perfect? Naah. Slow at times, outdated in others, and its emphasis on difficult, yet tedious and uneventful, space travel had more implications when every shuttle launch was a risk. Myself, having grown up with Star Wars and Star Trek, enjoyed this like a breath of fresh air. This was an adventure in a space filled with mysteries and implications, and I was glad I came along.