An excellent presentation on Nitrox. It will help you to understand the different types, uses and limitations of these mixed gases. You are given information from several sources, such as, NOAA and U.S. Navy. The information is NOT just someone's theory or speculation. The U.S. Navy has been researching and developing the science of Diving for more than 100 years. This is not a tedious, hard read. The presentation is quick, somewhat simple but not simplistic and with charts or graphs to use to help you develop a plan for your next deeper and/or longer dive. Informing you of problems, dangers and complications with using Nitrox (as well as plain air). Scuba Schools International (SSI) has done a good job putting this together. The earlier edition was good and very informative, but this edition has very much improved on the older edition. You need to understand that this is the text book they use in their Nitrox course, so if you plan to take the course from a SSI instructor there is no reason to buy this book outside the course. However, if you are someone who wants to expand your understanding of Nitrox then this is a good source even if you have read or own a copy of the U.S. Navy Divers Manual. This SSI's Manual on Nitrox brings you information from several time tested and improved sources and puts it together in an easily digestible form.