The green cover book is the OLD outdated edition. Check which sellers - In "See All Buying Options - offer the new BLUE cover edition with two divers on the blue cover. This book is for all scuba divers and those interested in diving, regardless of diving certification level or academic background. The purpose is to present the interesting concepts behind the physiology, so all can understand and enjoy.Topics in each chapter were selected from questions divers ask most frequently. In non-technical language this book explains the mysterious terminology of decompression tables and computers, reasons for the interesting changes in your body underwater, effects of diving in cold water and in hot conditions, the interesting hows and whys behind diving maladies, how to get in shape for diving, and important nutrition topics for divers. Although most scuba books have sections only about women, this book includes issues for men divers, too. There is a large, annotated glossary at the end of the book. More than a handy reference of definitions, it includes word derivations, key concepts, and fun stories behind the people and information.With the information in this book you will be better equipped to make sense of the many claims and counterclaims in diving physiology. You will be better prepared to understand more advanced training classes. You will have information to make informed decisions concerning decompression tables and computers, be a healthier, fitter diver, and avoid diving injuries. You'll even learn neat scuba knowledge tidbits just for fun. - from Amzon