The basis of this examination of the Blues was illustrated against the broader history of the United States itself. In particular, the oppression of blacks in America through history: Slavery, Jim Crow, Segregation, ghetto life, and modern racism and tacit and explicit inequality. This gave the story a powerful context, creating a meaningful backdrop for the subject of the book. This was the book's best feature. The research seemed solid enough, but, appeared to focus on only the most prominent performers of any given era.
When the Blues (the music) itself and (some of) the people who made it were explored, against their historical frame of reference, a tension was created. This tension was pleasingly, though, not powerfully enough, sustained throughout the book. This opened the door to make cultural insights.
Sadly, the insights were very sparse and weak. And the level of the tension never rose beyond a very weak level either. This gave the narrative little momentum or intrigue.
Additionally, the author decidedly made an effort to avoid any technical information. That is to say that there was no descriptive information about the music itself; its structure or composition. This also added to the book's perceived lethargy. Instead, some (but not much) focus was placed on describing the various musical ensembles themselves.
Finally, the chronology of the Blues and its many personalities was blurry and unsatisfying. In one passage the author would talk about the 1930s, in the next the 20s, then the 30s again, then 1940-1950. It was hard to keep the history and chain of events clear.
All told, the book does a good job exploring the characters behind the music and places them well in history. But lack of technical depth, and lack of breadth within the blues world itself coupled with confusing chronology and lack of insight made the read somewhat tedious.