Reddit mentions of Joy of Improv, Book 1

For improvisation, Dave Frank's Joy of Improv books are good for working through. Here's his full DVD going over the very basics.

For comping and jazz harmony in general, Matt Levine's Jazz Piano Book.

You can begin improvisation NOW. Don't wait until you're ready. You're plenty ready. Start with just the 1 and 5 chords of a key. Create a progression like (one measure each): 1--5--5--1. Use only chord tones in your RH, remembering to vary the rhythms and repeat notes, LH just playing chords at first.

Then try a 1--4--5--1 progression, again creating melodies with only chord tones at first. Then learn a blues in 2-3 different keys. Learn the blues scale and some simple LH patterns. Add a 7th to your chords. Then add chromatic and diatonic neighbor tones to your improvising.

Listen to great pianists like Wynton Kelly, Otis Spann, Oscar Peterson, Herbie Hancock, Bruce Hornsby, Billy Joel, Cory Henry, etc. and try to figure out parts of what they play that sounds cool to you. Write it down in a notebook and learn it in many keys and practicing applying it to everything. Then start sitting in on blues jams in your area. Most of those just are guitarists showing off all their pentatonic stuff, so they'll be happy to have a pianist, probably. Besides, you need performance opportunities to motivate yourself and learn. Record every performance you do.

Dave Frank's [Joy of Improv] (http://www.amazon.com/Joy-Improv-Book-Dave-Frank/dp/0793578779) book would be a great choice to build up your chops and improv abilities.

Besides those things, sightread through some pieces from Anna Magdalena Bach, lots of Martha Mier books (she write great pedagogical piano pieces), Bach 2-part inventions, maybe some Chopin mazurkas if you can handle it.

What is your goal? To play with blues bands? Pop/Rock groups? Jam bands? Classical solo piano? Worship pianist at church? Your practice division will depend on what you want to accomplish.