Reddit mentions of Jazz Theory Resources: Volume 2

forums.allaboutjazz.com

jazzguitar.be/forum

Learn how to use google site search to search those forums for topics that you're currently working on.

musictheory.net - use the lessons and exercises because you have to know the basics of reading and memorize the key signatures, etc.

I urge you to check out Hal Galper and Mike Longo's books/videos. They are at the forefront of Jazz Education and their material is a rite of passage for beginning jazz musicians.

Here's a playlist of Galper's masterclass videos:
http://www.youtube.com/playlist?list=PL7iWyGibrnPOQPEuUL4O3s5E0qdPj-cqs

The best general jazz chord-scale theory text I've seen (I've seen them all) is probably the Berklee book,
Chord Scale Theory and Jazz Harmony;
However, even better would be the Bert Ligon books, because they go into more detail about how to actually put it into practice:
Connecting Chords with Linear Harmony
Jazz Theory Resources Volume 1
Jazz Theory Resources Volume 2
Comprehensive Technique for Jazz Musicians


P.S. this subreddit is geared more towards jazz listeners and may not have that many musicians.

Depends what gaps you have. Standard classical theory is good enough for functional jazz harmony, although some terms are different. (No augmented 6ths or neapolitan chords in jazz; but lots of "tritone subs".)

[Jazzology] (https://www.amazon.co.uk/Jazzology-Encyclopedia-Jazz-Theory-Musicians/dp/0634086782) is a good survey of functional jazz harmony. It's somewhat dry in presentation, and it's a shame that all the examples of tunes (melody and chords) are written by the authors, not taken from jazz standards.

For post-functional jazz theory (modes and chord-scales), Mark Levine's [Jazz Theory Book] (https://www.amazon.co.uk/Jazz-Theory-Book-Mark-Levine/dp/1883217040/ref=sr_1_2?s=books&ie=UTF8&qid=1499166438&sr=1-2&keywords=jazz+theory+book) is the bible. As a standalone jazz theory text it has many drawbacks, which is what provoked Rawlins to produce the above book. So you could see them as companion texts.
The two great advantages of Levine's book are its easy readability and presentation, and its many quotes from jazz recordings (mainly chord voicings and licks from improvisations). However, Levine's interpretation of those quotes should be taken with a pinch of salt: he uses them to support his chord-scale theories, but they can be interpreted in other ways. It's by no means clear the players themselves thought in those terms.
A great scathing criticism of chord-scale theory can be heard [here] (https://www.youtube.com/watch?v=NehOx1JsuT4) (Not as a theoretical principle, note, merely as a system for improvisation.)

Bert Ligon's books are also highly respected - I see them recommended all the time, although I haven't read any myself. [This] (https://www.amazon.co.uk/JAZZ-THEORY-RESOURCES-1-BOOK/dp/0634038613/ref=pd_sim_14_1?_encoding=UTF8&psc=1&refRID=TK8Y6EQRPH62NAYVHB2G) is probably the best, and there is a [volume 2] (https://www.amazon.co.uk/Jazz-Theory-Resources-Harmonic-Organization/dp/0634038621/ref=sr_1_3?s=books&ie=UTF8&qid=1499166895&sr=1-3&keywords=bert+ligon).

In short, one gets the impression that "jazz theory" is a live body of knowledge that is still being worked out. Different authorities have different views and perspectives. In particular there is a tension between how the players themselves think (especially older ones), and how academics analyze the music produced. After all, the period of jazz that many people hold up as the zenith (the bebop era) was produced by musicians whose jazz training was on the bandstand, by example from older players. Some may have studied music at conservatoires, but it would have been exclusively classical theory. "Jazz" was learned by ear.