honestly...i would recommend lessons. i know the analogy isnt exact...but think about the difference between reading Phil Hellmuth's books and posting hands on 2+2. Most (non-academic) music theory books read at the same level as "Play Poker Like the Pros." and the seriously academic classical texts (those by Schoenberg, Piston, etc etc etc) dont necessarily have much bearing on what you're trying to accomplish. i think its really important to have someone to talk to about music, especially if you're interested in theoretical concepts.

it took me months to understand what a tritone substitution was. if i had thought to even mention it to my teacher at the time, he would have just said "dominant 7th chords a tritone apart share the same 3rd and 7th. the 3rd of one is the 7th of the other, and vice versa. and since the 3rd and the 7th are the important notes of the chord...you can substitute F#7 for C7, if you feel appropriately inspired."

so...i know you dont want to pay for private lessons....but i think you should reconsider. find someone who's young, talented, and up-to-date on modern music, and the lessons will be well worth the money.

jon