This is one of the better books coming from Berklee Press as it does not try to summarise everything about jazz in 100 pages, like Berklee Jazz Piano BK/CD. Blues licks are presented in many keys with great recorded examples by the musicians at Berklee for backing tracks for your soloing workout.
You start small with one-bar ideas and then grow to be able to play solos based on longer phrases. You can actually play, remember, and apply the examples - very well taught. Note however, that the book is usable for any C instruments so there are no piano voicings for piano students, only single line lead sheets - a great pity for piano students, but not the end of the world. Print quality and the organisation of the book are excellent.
Listening to the band comping without the soloist is an education on its own. Many different types of blues and jazz grooves are recorded in a many keys. Absolutley great for your learning and understanding. Its a great pity they didn't provide some written piano comps for the tracks/lead sheets.
With excercises in so many keys, you'll probably skip the less common keys, especially as there is some repetition of licks and motives accross the book. If you are playing rock, funk or fusion with your own band, you might gravitate to rock keys like E, A, D, which can be played easily if guitar is your instrument. If you are focusing on jazz, you'll tend to pick drills in other keys. I avoided C# as life is too short to learn blues in this key (hang on a second, the book shows that this key is related to E major, better go check that out!).
All in all a valuable learning book with great solos, interesting backing tracks, and really well structured to allow you to work through to master the blues.