Adobe's Digital Editions (http://www.adobe.com/products/digitaleditions/) would be my starting point. Of course, the decision ultimately relies on how many you're going to sell ( <500 a month you can manually do these and save coin, more than that you'd want 100% automated and take the hit because you're dealing in bulk).

If I may also suggest an unconventional distribution tactic, you can go the Paulo Coelho route (http://torrentfreak.com/alchemist-author-pirates-own-books-0...) and release the PDF on the torrent sites to build awareness, since that's one of the biggest challenges.