Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Greatest book on blues; film also exists

This book is known as the finest book on blues ever written. I enjoyed it thoroughly and recommend it as a necessary reading for anyone seriously interested in the blues. A film based on the book came out in 1991 or 1992, but it is impossible to find; it was a documentary produced by Dave Stewart of the Eurythmics, directed by Robert Mugge, and narrated by Palmer, who also produced the film's soundtrack of Mississippi blues artists. Wish someone would release that on video -- I want a copy!!