I agree with you when you stated - "There's probably no such thing as a best drawing book. Everyone has a different learning style which is why there are always new drawing books coming out." I've found that for myself as my drawing skills progressed I would still reference some of the 1st books I bought but would go out and look for new and different books with techniques / tips.

I'm more a visual learner where my dad (who also likes to draw) is more of a step-by-step type of person.