This book is a sweeping overview of the Yoga tradition of India and its many subdivisions. He covers everything from Tantra yoga, Karma yoga to Sri Aurobindo and everything in between.
Does he do a good job at presenting this vast subject?
Yes and no. Yes he covers the various topics in some detail. Though his coverage is spotty. On some topics he does a good job and on others he glosses over. He also suffers though from accepting every guru and school as valid. As such he includes several well known cults and bogus teachers as legitimate.
He also does not cover the problems with gurus in the yoga tradition. A good many of them have sexually or emotionally abused their student and had to leave the schools they founded. The kundalini teachers are especially notorious in this regards.
Also does not adequately cover the so-called 'crazy wisdom' teaching and how it is abused.
Two cases of his intellectual sloppiness stand out:
Adi Da(franklin Jones)- a brutal authoritarian with a god complex, Fuerstein gives a glowing review of his teachings and him as a authentic guru. Da's group is considered a cult by all cult-watch organizations. BTW Fuerstein was/is a student of Da.
Yogi Bhahan. This man is teaching a mish-mash system of yoga with no lineage. The Sikh's don't even do yoga in India. It is also considered a cult. Yet georg includes his teaching as valid.
His inclusion of these two groups makes me wonder if he really does investigate and research the various schools of yoga or accepts what they say on face value.
As such this work is marred by dubious scholarship. Ken Wilber's glowing comments not withstanding.
Despite this it is still worth purchasing. But don't accept it on his say so alone, do some research.