On the surface it's an engaging fictional story about an old man who knows the answers to literally all of the Big Mysteries of life -- everything from God to gravity to the bizarre qualities of the speed of light. The old man even explains how they all fit neatly together. Adams uses what he calls "the skeptic's trick" along with some hypnosis techniques (Adams is a trained hypnotist) to make the old man's fictional explanation of reality so simple and believable that you'll have fun trying to figure out what's wrong with it.