I'm not sure if I understand 100% - you're charging 1btc for any kindle ebook under $30? If so, that's a great deal, and I will probably be buying from you! When you say they are deDRMed, are they in .azw or .mobi format? Why do you need the buyers bitcoin address in the message body?
1. Yes, I am charging 1btc for any kindle ebook under $30
2. I will keep the original format, which means mobi or tpz.
3. Since I never make a deal using BTC before, if requiring your bitcoin address bothered you, I will delete this line.