The book is primarily a criticism of 'traditional' school-based learning methodologies, using observations of children playing video games and the author's own play sessions as representative examples of the 36 principles of good learning he describes. He uses primarily 3d shooters and RPGs as his examples of 'good' video games (meaning that they encourage learning things about and within the world of the game). The author defines and conceptualizes his principles of learning and contrasts it with the school-based education process, noting the vast differences between the two. On this topic of criticism of school-based education, the author makes a strong argument.
His second argument, that these principles missing in school are demonstrably present in video games, is very vague and unfulfilling. The author often stresses elements of learning that can easily be found everywhere in life and social activity and in other forms of media, not just in video games. One point he makes in the middle of the book about incremental difficulty and the player's dynamic 'regime of competence' was a good topic consistent with video game design (although easily found in other places, such as golf handicaps), but it was not good enough to warrant his emphasis on video games in the other ~150 pages of the book. He repeatedly mentions that kids enjoy playing video games but don't enjoy learning in school and suggests that school should be like playing a video game, but he leaves it at that. Because he focuses on the process of learning and assumes videogame content and classroom content to be of an equal nature, the burning question of how to make learning calculus equations as fun and desirable to learn as advanced combat strategies to annihilate your friends in Starcraft remains unfortunately beyond the scope of this book.
If the intention of the book was to show that video games have the capability to encourage learning of arbitrary content, it succeeded. However, watching TV or movies or playing non-video games with your peers can be just as conducive to learning (and, depending on the content, just as mind-numbing). Having been weaned on Mario and Zelda myself and already appreciating the incredible complexity and carefully tuned learning curve of videogames, this book was somewhat interesting for its general theory of education but not as thought-provoking regarding video game theory as I had hoped.
This book is probably a better read for older generations that didn't have video games as an integral source of learning during their formative years and have as a result never taken them seriously.