Great question.
First of all, I'm a hobbyist bass player, with no interest in playing out. I've been at it for a couple of years, and my skill level is intermediate in some areas, not so great in others. In particular I never mastered the fretboard and my understanding of theory was hazy. I can read music pretty well, but found myself looking at tabs too much rather than build my skills.
I took private lessons for a year with a well-regarded instructor in Atlanta. No doubt my playing improved, but as I look back, the theory part of it was a weak link. The instructor would give me exercises to work on, like constructing walking lines, but didn't explain the reasoning behind it. Perhaps it was because he knew it so well himself that he had forgotten how hard it was to learn initially. It may have been partially my fault as well, as I told the instructor up front that my (modest) goal was to be able to play along with songs. So I learned to play a lot of songs, but was not good at any sort of improvisation.
I happened upon the book by chance as I was browsing Amazon. I already had 10 or so books, including some theory ones, but it still was not sinking in. I was starting to become frustrated as I felt I was in a rut. I was spending too much time playing along with tabs. I knew this was a losing approach, but didn't want to take more private lessons and the books I had were not doing it for me.
The Cap course appeals to me because of it's structure and incremental approach. You will improve both your fundamentals and technique if you put in the work. Ariane doesn't sugar coat the effort involved, but explains in the most pleasant way how to do it in manageable chunks. I'm impressed (as are many others.)
