This book is about float tanks. If you have seen the movie Altered States, that is a float tank. It is an isolation tank where you float in a body temperature saline solution to remove as much stimulation as possible. This book details the research done (up to about 1983) on float tanks, and its health benefits. The book is essentially a commercial for float tanks. The primary benefit is related to the fact that float tanks make it much easier to reach states of consciousness normally reserved for experienced meditators - lower stress, more creativity, general well-being, pain reduction, improved learning (this one I am sceptical, because there is a large body of evidence that recall is tied to the state of consciousness you are in, so learning in the theta brainwave state doesn't translate to the beta state effectively), recreational hallucinations, peak mystical experiences, etc.