Hi Sharon...the book can be purchased in a couple places. We bought ours from the GUE site, but it is also available online in either a PDF or soft cover from the other link below. In both cases the prices are in US funds.
http://www.gue.com/?q=en/node/163
http://www.divefitness.com/html/guides.html
-this second link has a couple excerpts from the book to give you an idea of what its all about.