It really depends on your target market. Like what kind of crypto books will you sell? will it be for beginners or will it be for advanced users?
For example, if your book is about the basics of blockchain and cryptocurrency, it's not possible to sell them only via BTC, ETH, or other alt coins. It's still best to use a basic payment method like credit/debit cards.
And if let's say, an advanced user would like to purchase a book about blockchain and cryptocurrency, i doubt if they'll even purchase a book for added knowledge when there are a lot of podcasts and research materials available for free just by searching via google. But of course, I might be wrong. Just sharing my own opinion.