Reddit mentions of Jazz Keyboard Harmony: A Practical Voicing Method for All Musicians, Spiral-Bound Book & CD

Ideally, you'd find a Jazz teacher who can step you up from the basics, but, if that's not the case:

First, if your core music theory is not solid, take a few weeks to brush up on that. Make sure you understand and can play:

- Major Chords & Inversions (i.e. C E G for C Major)

- Minor Chords & Inversions (i.e. C Eb G for C Minor)

- Dominant 7th Chords and Inversions (i.e. C E G Bb for C7)

- Memorize the circle of fifths (though in 4ths, which is much more applicable in Jazz - this is just in reverse - C F Bb Eb Ab Db Gb B E A D G) - this will show up everywhere in jazz, including the first book I'll recommend.

Now onto the jazz stuff:

1. Learn Jazz Harmony first. This starts with Shell voicings and guide tone chords. An excellent book here is the Phil Degreg book "Jazz Keyboard Harmony" It starts with the most basic shell voicings and builds upon those voicings note by note, and explicit step step instructions on how to practice and what to practice with plenty of exercises and play along tracks.
   
2. Once you learn a voicing type, pop open a fake book. Play tunes using those voicings. Grab software like iRealPro to have something to play along with. If you use shell voicings, play the melody in your right hand.
   
3. Going beyond just harmony, use a backing track from software such as iRealPro and play the melodies. Start improvising little by little on those melodies. Learn your jazz scales and try a course like Gary Burton's Jazz Improvisation on Coursera (you can audit this for free) to go beyond just tinkering around. I would not recommending doing this course until you at least have shell and guide tone voicings down.
   
4. If you don't have iRealPro or something similar, record yourself playing your own harmony in guide tone chords, and improvise your own melodies on top.
   
   I'm a hobbyist, not a professional, but this helped me immensely understand jazz quite a bit more.
   
   Obviously advice like "Listen to jazz and try to transcribe" is good too, but that will make you hit frustrating walls if you have nowhere to start. Also, do not get "The Jazz Piano Book" by Mark Levine - it's more of a reference text, NOT a step by step learning book - even if someone recommends it - it's not for beginners.

A fake book is a book of tunes that just contains a lead sheet, with only the melody and chords (usually). Best example is of a fake book is (wittily named) The Real Book, which pretty much any jazz musician uses religiously.

To the OP: There is absolutely no substitute for taking legit lessons from a teacher who specializes in jazz. If you can play jazz well, you can play any non-classicaly genre (and it sounds like you already know how to play classical anyways). In the absence of good jazz instruction, you need to just play a shit-ton of chord voicings in every key and mode you can think of until you can fire off voicings for any chord progressions without having to move your hand all over the piano after every chord. If you want an especially good resource to teach you how to do this, the book I learned on is here. It gets boring as hell, but be able to do anything in that book from memory, and you'll have a really solid foundation for comping chords and putting a decently embellished melody over them.

Oh, also learn how to walk a bass line.

My piano teacher recommended this to me: https://www.amazon.com/Jazz-Keyboard-Harmony-Practical-Spiral-Bound/dp/1562240692/ref=asc_df_1562240692/?tag=hyprod-20&linkCode=df0&hvadid=312057344057&hvpos=1o1&hvnetw=g&hvrand=365158453909601890&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003231&hvtargid=pla-452702816110&psc=1

I just got it the other day and it's great. I have the Levine book too but I think that's more of a reference material rather than a practical guide to how to learn. I highly recommend the linked book.

I've seen some positive recommendations for this book but haven't used and don't own.