First, let me recommend watching the movie before reading the book. The book is much more powerful after you have tried to puzzle the meaning of the monolith for yourself. Then, if you did not understand the movie, or want clarification on certain points, this book is the place to turn. It answered my two main questions: "What did the story of HAL 9000 have to do with the story of the monolith?" and "What did the ending mean?"
Unless you are a fan of the old school of "hard" science fiction, you'll probably be annoyed by Clarke's overly-expository writing style and obsessive devotion to scientific accuracy. This story was obviously written when the science was much more important than the fiction. At times, it reads like an astronomy textbook. But, in the end, all your questions from the movie will be answered. If you like the answers, you'll like the book. If you enjoyed "figuring out" the movie, the book will spoil the mystery for you.
In the final analysis, this novel deserves high marks because without it the classic film would never have been made, or at least would have turned out much differently. In his companion book "The Lost Worlds of 2001," Clarke describes how the movie and novel were developed simultaneously with feedback in both directions. Clarke would write a chunk of the story, Kubrick would film it, then Clarke would revise what he had written to parallel the movie. Both Clarke and Kubrick wanted the movie and the novel to be viewed as one collaborative effort, even though there are some minor discrepancies between the two. The story was originally inspired by Clarke's much older short story "The Sentinel".