The 2001 book is interesting in that it's not an adaption, nor did it inspire the original film. It was actually written co-currently with the film's production, giving the two a somewhat symbiotic relationship. Of course, Clarke would go on to right a few sequels, thus expanding upon the film greatly.
In any event, everyone likes monkeys, right?
Author: Arthur C. Clarke • Year: 1968 • Info:Wikipedia