I was astonished to find I had reviewed this book in 2002
https://www.amazon.com/gp/customer-reviews/RMFH36FE9TI5Y/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=0812690257
John C. Landon
5.0 out of 5 stars A distorted history
Reviewed in the United States on January 21, 2002
This invaluable study of the history of the text of the Gita is unfortunately out of print, but a must read for anyone interested in unraveling the enigmas of Indian spiritual history and wresting the gold from the illusions here. Attempting to show that the book we now have is a very late version from the period ca. 800 A.D. with a theistic cast not present in the original, the book also uncovers the connection with the Samkhya tradition, a very early form of which was probably part of Gautama’s path. As if the text of the Iliad had fallen into Christian revisionism and made a document of spiritual monotheism, the Gita that we have is an eloquent but misleading series of confusing layers. The author also suggests certain interpolations in the text of the Yoga Sutras designed to make it seem compatible with the tide of monotheism sweeping India in the later medieval period.
Cf. also a work such as Gerald Larsen’s Classical Samkhya, for the difficult history of this uniquely interesting yoga, and its tortuous history.
New Man, New Age, New Socialism 