For the price, I got everything I needed out of this book. It definitely improved my dexterity and in particular got me using my 4th finger. Very useful if you want to move on to playing a lot of octaves, such as in slap and pop or funk/fusion techniques.
However, I never got to finish the book - the exercises are a bit boring and it came down to deciding I could spend the time more usefully practising something else. But, overall, I'm glad I did it - I've got a strong fretting hand now!
- (Huddersfield, United Kingdom)