This is a good starter book for people who are not otherwise familiar with the basic poker math behind pot odds, implied odds, calculating equity, etc. There is also a wide range of general poker concepts that can be helpful to beginners and even intermediate players.
The greatest asset of this book is explaining concepts in a simple way that is easy to understand, with numerous examples of situations that show practical usage. Generally, even for knowledgeable players who have been unprofitable at the table, this is good reading to make sure you are covering the basics and not throwing away $ needlessly without being compensated appropriately.
My main critique is that the book is fairly short, coming in at just over 100 pages. However, I believe there is an extended edition that expands on the concepts in the shorter version, so this would be edition-dependent.