Although I found a few ideas contained in the book useful, I did not like the concept nor the approach. For a start, the 21 things structure was quite confusing at the beginning, when the author kept introducing numbered sub-sections within the main sections and I was not sure what I was reading about at each time.
I found some of the thoughts patronising and dismissive of other people's approach and/or struggles to engage in regular practice and other aspects of their lives. I would have omitted the section on "finding love", as at that point I felt like I was reading a dating manual, completely irrelevant to the practice of Ashtanga. I did not like the section on "excuses" that other people may have not to practice and the author's attitude towards this, making fun of people's reasons. The superficial reasons she describes -too lightly and judgmentally in my opinion- may be underlying other stronger reasons and each of us has to follow our own journey into the practice.
There were a few other comments, opinions and sections, particularly the ones in which the author suggests ideas of how people should/could improve their lives that were too subjective and judgmental, but I guess, opinions are something very personal, including my own. I am a beginner in Ashtanga, and I had done my reading and searches into the main sources (and I continue to do so), which is what probably most people do.This book did not help or add anything to my knowledge or practice. The only thing I did find useful was the chapter about mysore, as I have not been there yet, explaining some of the elements of the practice and accreditation.