I love this book. Gail Johnson has taken me from loving this style of music to being able to actually play it. She's just done a fantastic job of introducing and teaching funk keyboards.
The book comes with a companion CD, which is very useful, as the notation is fairly complex, and I find it quite helpful to also hear the parts and play along with them. After a few repeats of each exercise, the recorded keyboard drops out, and if you're playing along and there's no apparent transition, you know you've nailed it.
I will spend weeks digesting this, getting facile with it, learning it in various keys, and integrating it into my playing. The cost is miniscule compared to the value.
If you love funk keyboards but haven't been able to work out how to play them just by listening or you don't know someone who can show you this stuff, this book is for you. I just wish I had had it 20 years ago.
The only change I would request is for her to add extra audio tracks of the complete songs that go at maybe half speed. It's taking me quite a while even to learn a couple measures of the best stuff and bring it up to full speed. I'd like to be able to play along sooner, at a more manageable speed.