I think .pdf in addition to .epub is a must.
If you have different formats, offer them separately. Most readers need only one.
I would do pricing in mBTC, as long as bitcoin is that valuable.
I wish you the very best with your venture!
Yep, heard the file format thing a bunch, currently processing PDF, ePub and mobi.
I _want_ to do mBTC but I need my currency converter and Bitpay to accept it as a single unit of currency before it makes sense. I might try to do somethign where the price data is in BTC but the display is in mBTC, but so far I'm hearing that adds even more confusion for potential shoppers...