Recently I felt happy and honored when some of my most sincere students asked me which book do I recommend on the Yoga topic at hand. This is my answer in general.
To start with, one who wants to buy or read a book has to know why they want a book on a given topic. If they want to just collect some pieces to create a collage for a school project that is not much relevant later, they might need an Encyclopedic or thickest looking book!
If they want to learn how to do certain practices, most of the books will be insufficient. Practice has to be learnt from an experienced teacher and practiced for a sufficient time. Only after that a book may be useful. Most of the Yoga books are less than effective for most of the Yoga students who have not done a lot of practice!
If they want to get an accurate understanding of a given text such as a scripture, they must review the background of the writer in terms of language, scholarly work, opinions of others, education, etc. Choosing one particular author only because he/she is world famous or celebrity or the one who is expert in another related field will lead to in-accurate understanding of that given scripture. But, at the same time, some scriptures requires scholarly background along with practical experience. If the later is lacking, the textual understanding is useful as a translation but not as a practical guide.
But, one of the most important factors while choosing a book is the extent of time, interest, energy and dedication one has to spend on the book. If one has a very short time, the best large size book will be of no use. Or, if one has mild interest and one is reading a book on Anatomy that took the author to write 25 years will produce no anatomy student out of the reader.
Just knowing the language of the text, having the purchasing power, and being “born free” are not the real qualifications for studying a Yoga Book!