...but the special effects weren't up to it, so they changed it to Jupiter.
The book then leaps ahead a few million years to the year 1999, detailing Dr. Heywood Floyd's travel to Clavius Base on the Moon. Upon his arrival, Floyd attends a meeting. A lead scientist explains that they have found a magnetic disturbance in Tycho, one of the Moon's craters, designated Tycho Magnetic Anomaly One, or TMA-1. An excavation of the area has revealed a large black slab; it is precisely fashioned to a ratio of exactly 1:4:9, or 1²:2²:3²—that is to say that the thickness of the slab is exactly 1/4 of its width and 1/9 of its height. Such a construction rules out any naturally-occurring phenomena, and at three million years of age, it was not crafted by human hands. It is the first evidence for the existence of extraterrestrial intelligent life. Floyd and a team of scientists drive across the moon to actually view TMA-1. They arrive just as sunlight hits upon it for the first time in three million years. It then sends a piercing radio transmission to the far reaches of the solar system.
The signal is tracked to Japetus, one of the many moons of Saturn, where an expedition is then planned to investigate.
The book leaps forward 18 months to 2001 to the
Discovery One mission to Saturn. Dr. David Bowman and Dr. Francis Poole are the only conscious human beings aboard Discovery One spaceship. Their three other colleagues are in a state of suspended animation, to be awakened when they near Saturn. The HAL 9000, an artificially intelligent computer addressed as "Hal," maintains the ship and is a vital part of life aboard.
More:
http://en.wikipedia.org/wiki/2001:_A_Space_Odyssey_%28novel%29