by Ed Roseman
ISBN: 0966161661
Buy on Amazon
Found in 1 comment on Hacker News
I used this book as a gentle theory introduction: https://www.amazon.com/Edlys-Music-Theory-Practical-People/d...

Ideally you'd do this alongside a teacher or someone who knows more so you can bounce questions and applications off of.

There may be better theory books out now, I haven't kept up.