While the manual presents information in a clear and simple manner, it is still mind numbingly boring. Its cutesy illustrations intended to highlight important or related information are distracting and the overuse of intertextual and sidelight boxes chops the text up and interrupts the easy flow of information. SSI does do a good job of integrating the research behind the information into the book a a whole but sometimes this research is repeated in several places in case the reader wasn't astute enough to recall it from a previous chapter (this particular reader is astute enough, thank-you very much). And the bulk of the slim book is not about the practical application of actually using nitrox but instead reiterates the fact that it is in fact advantageous to use this gas over oxygen which the reader should ostensibly know if he or she has paid for the course that provides this manual. Maybe I'm unusual in my preference but I'd have been much happier with a booklet that cut to the chase instead. Of course, if you want to be certified through SSI to dive using nitrox, this is the only option. Just be ready to forcibly prop your eyelids open as you read along.