Reddit reviews Jazz - Harmonielehre. Theoretische Grundlagen.

I've had classical training on the piano for 10+ years, too, also on the church organ, and have only recently started to try and understand this new and modern thing called jazz.

I found Mark Levine's book on Jazz piano to be fairly nice and beginner friendly. Later on, I dove into a more theoretical and systematic German book that's more or less based on Berklee. I don't think it's been translated in english yet.