There are a number of e-book selling sites that allow authors to receive payment in cryptocurrency. Here are a few examples:
Pronoun: This platform allows authors to sell their e-books on major retailers like Amazon and Barnes & Noble, and receive payment in bitcoin, bitcoin cash, or ether.
E-junkie: This site allows authors to sell their e-books and other digital products directly to customers, and receive payment in bitcoin, litecoin, or dogecoin.
Selz: This platform allows authors to sell e-books and other digital products directly to customers, and receive payment in bitcoin, litecoin, or ethereum.
Gumroad: This site allows authors to sell e-books and other digital products directly to customers, and receive payment in bitcoin.
It's worth noting that while these sites allow authors to receive payment in cryptocurrency, they may also charge transaction fees or take a percentage of sales. It's important to carefully review the terms of service and pricing before using any of these platforms.