About Payhip ecommerce
From the site:
To start selling on Payhip, simply upload your ebook file and add a name, description, price and a thumbnail image. You can setup your ebook page and start earning in a matter of seconds.
Give customers an incentive to spread the word by letting them tweet and like your ebooks to get discounts… How does it work? Your customer clicks on a “Tweet or Like for Discount” button, a dialog pops up, pre-filled with a message and link — once they tweet or like, they get a discount.