Once you know some basic blues theory and have the five pentatonic minor scales in your fingers and know how to connect them together, playing up and down the neck in any key, then (and only then) a book like this is invaluable.
Like most people who reach this stage, I found myself being able to play some good sounding blues pieces but being rubbish at improvising... playing all the right notes but sounding dull and aimless. This book has 70 licks for either bars 1 & 2 or 3 & 4 or 5 & 6 or 7 & 8 or 9 & 10 or 11 & 12 of the 12 bar blues progession. Some are pretty easy, some pretty difficult and plenty in between. Rather than starting with lick 1 and learning them all consecutively, I have gone through the whole book learning the easy and medium/easy licks in each section... this means I can start playing them over the 12 bar blues backing tracks at the end of the CD, while working on the remaining medium/difficult and difficult licks.
Unlike another similar book/CD package I reviewed, I was relieved to find the CD plays the licks over a back beat, which means it is much much easier to learn the phrasing. Everything is in G... this is also good as it means you can practice connecting all the licks with each other. But once in the fingers and memory, the next stage will be transposing them to other keys. Although some of the licks are fast, with sixteenth notes or shorter, everything is played over a pretty slow blues progression. Go to a pub and start jamming and you may find you have to ask the other band members to slow things right down... the licks in this book are more for playing mellow blues BB King style rather than for jamming over faster pieces. I like this... at some stage there'll be more work for me, learning to play wilder stuff... but learning the blues is a never ending process, it's important both to make progress and to enjoy the journey - this book enables me to do both.
One practical gripe - each lick is a track on the CD and starts with a few seconds silence, which is perfect, but the nano-second the lick finishes the CD moves on to the silence at the start of the next track. If you decide you want to play your original lick again you have to remember to double-press the back button to get back to the start of that track - keeping pressing it just the once and you'll keep going back just a second or two to the start of the subsequent one. Sounds hardly worth mentioning? You're right, it's very minor indeed, but irritating nevertheless!
Anyway, that one thing aside, if you are at the guitar-learning stage I describe at the top of this review, the stage I am at, then this book is the near-perfect tool to help you move your improvisation on to a much more dynamic level.