An alien artifact teaches a man-ape to use tools. Heywood Floyd goes to the moon to investigate a mysterious situation. Dave Bowman and his crewmates, most of them in cryogenic sleep, head toward Saturn....
Let me get my two big gripes out of the way first.
1. Arthur C. Clarke's characters are cardboard cutouts and largely interchangeable with one another.
2. Arthur C. Clarke's prose doesn't bring all the boys to the yard.
Now that I've got that out of the way, I enjoyed this book very much. Some of it is a little dated, not surprising since Clarke wrote it around the time some man-ape discovered fire. A lot of it is spot-on, though, like Heywood Floyd's tablet by another name.
The first two threads do a great job of setting up the third. The man-ape thread was the least exciting but nicely set the stage. By the time Bowman's thread got going, the book was very hard to put down.
Unlike a lot of sf classics, I enjoyed both the story AND the concepts. Because of the enjoyment factor and because it's a classic of the genre, I bumped it from my original 3.5 to a full 4 out of 5.