Let me just start off by saying that this book is completely obviously a treasure trove of information for people curious about blues lineages or who'd like to learn more about the "discovery" of the now-canonical old blues figures like Son House, Muddy Waters, Blind Lemon Jefferson, and many more. I say discovery in quotation marks because for the most part, these musicians were already relatively well-known within their own communities, but Alan Lomax was the first to go into all these small, isolated communities in Mississippi and record these artists, an act which down the line brought blues music to the attention of the mainstream. Lomax wrote this book in his old age looking back on his experiences recording these artists: he knows he's the shit, you know he's the shit, and that's that.
This is what I was expecting, and this is basically what I got. Lomax is clearly incredibly passionate about this music, and his memories are vivid and clearly told. Also, as the father of modern ethnomusicology, he has the analytic skills to describe the logistics of how the MUSIC of blues music works and draw comparisons to African music, and describe how it differs or is similar to that of other communities. In this respect the book was highly fulfilling. There are a number of compilations of Lomax's work which is covered in this book which I found incredibly rewarding to listen to in conjunction with reading the book (namely "Mississippi: The Blues Lineage" and "Classic Blues" from the Smithsonian Folkways label. Additionally there is literally a partner CD to the book but I wasn't able to get a hold of it through the library system, so I can't comment on it.) This information would be useful to a long-term blues listener just as much as someone engaging with the music for the first time.
I wasn't really expecting this book to be so illuminative of the experience of poor blacks in the Jim Crow South. As a man of liberal allegiances, Lomax's stories about the difficulty of entering communities and speaking to black people are told with lucidity and a fierce sense of social justice. On these plantations, and in the prisons and work-camps, Lomax was uniquely positioned to see the realities of these situations. His reflections are rare glimpses into a fascinating underbelly of American society, one which in mainstream history is still mostly swept under the carpet-- after slaves had technically been freed, but before any efforts had been made to revise the social order in the South.