Try using
http://satoshibox.com. It is very easy to use all you need is upload your ebook and send your links to potential buyers. They can't download it if they didn't pay.
Also try cryptothrift.com I saw some books has been sold there.
I was going to suggest satoshibox too. Beware though as soon as someone has a digital copy of your book they will likely just leak or share it but I guess that's something you'll just have to deal with. Good luck.