Mann's book begins by laying a basic groundwork in chords, scales, bass lines, and theory, and then moves on to cover the differences between various styles. There is enormous ground in between that is left uncovered, and I was unable to get much out of this book despite doing the exercises and listening to the accompanying CD. The book doesn't have enough examples fully written out, and the examples on the CD are too difficult for a beginner to imitate (though I will admit the possibility that I simply don't have the talent...). Mann should have taken us step by step, adding one element then the next, and showed us the steps in music notation as well as by example.
The book lacks a discography, despite Mann's repeated exhortations to listen to blues performed live and in recordings.
On the other hand, the musicianship on the CD is excellent, and includes half a dozen example performances in various styles that are worthy of an audio CD by themselves. Mann clearly knows his material, and has a background imparting it to others in person.