By far the best resource for learning (useful) music theory, and not wallowing in useless scale-excercises (in 99% of the theory-books out there), would be Carolkaye.com. Not trying to be overly dismissive of the prevailing way of learning, but I tried both ways, and Carol’s chordal methods are FAR more effective towards becoming a good musician, than learning scale-notes/excercises. This is from my personal experience as a player and a teacher. Up until around the late 60’s, this was the way everybody learned music structure/theory. Chordal-learning is also a lot more fun…

Hope this helps!

Good luck!