2001 is one of the finest science-fiction books I've ever read. The book starts off millions of years ago - when there was no man, only a primate-like "Man-Ape". A mysterious object from space arrives on the Earth - and influences the brain patterns of the Man-Apes. The Man-Apes were almost at the point of extinction, but because of the powers of the object from space, they survive and evolve into Man.
Present timeline - there's concern about a mysterious object that was discovered on the moon. It seems to be atleast three million years old. It is perfectly black, in perfect geometric proportions (1:4:9), and shows absolutely no sign of damage. It was discovered due to the unusual magnetic field it created, and so it is designated T.M.A.-1 (Tycho Magnetic Anomaly - 1). A group of scientists go to the moon and try to find out what exactly it is - and how it got there.
While T.M.A.-1 is being observed, it's quiet for a while - but suddenly, a powerful blast of energy is emitted. This seems to be a very strong signal that was transmitted for a purpose, probably to be intercepted by intelligent beings somewhere in the galaxy, or beyond.
The space ship Discovery is bound for Saturn - on board are some cryogenically frozen men, along with David Bowman and Frank Poole, and an intelligent, self-conscious computer called HAL 9000 (Heuristically Programmed Algorithmic Computer). Except HAL, the voyagers are unaware of Discovery's true mission. The signal that T.M.A.-1 emitted was traced to somewhere near Saturn, and that's why the ship is being sent there.
The journey's two stages - a crucial manoeuvre near Jupiter, and then the voyage to Saturn is thrilling, to say the least - Clarke describes all this so well. Finally, the secret of T.M.A.-1 (and there is a T.M.A.-2 in the story as well...) is revealed in the book's fascinating last chapters.
This is an extremely well-written fascinating story. And considering that it was written before man actually landed on the moon, it has to be appreciated for the extent of detail that is there. I have not seen the movie based on this book, but it is supposed to be slightly different from this story. A number of sequels (books and movies) followed.