Pros: Covers all of the details,
Cons: can be technical with the language
To clarify, the price paid covered the book as well as the introductory class that went to about NFP. This is a great system to use that does not need thermometers, nor internal tests to determine fertility. It is based solely on external observations and consistent charting. This really allows a husband and wife to be in deeper communication about sex and her body. The book is usually only available if you take the class that goes with it and/or meet with an instructor. The book is very useful, but an instructor can really put it all together for you and answer questions.