As Well I have Read and still continue to read and use the entire grimouire series of books, Bass,guitar,keyboards, chord encyclopedia, scales and modes and progression theory, they are all Excelent tools, the best I've ever seen.

THE Reference for scales and modes.

The first section can be a bit daunting, but I found it helped my understanding of scale and mode construction immensely.

Each scale also has a list of chords that the scale can fit with. I refer to it quite a bit for what scales go with what chords (or vice versa). It also lists modes for each and every scale.

I'd buy it again if I had to replace it. I say it is suitable for all skill levels, but I would imagine it would really be best used by intermediate players on up.