A book sold is a book sold. Not everybody uses bitcoin and I don't want to be a gatekeeper. And neither my book nor The Sovereign Individual are strictly Bitcoin books anyway. But I obviously prefer if sales came directly through my site and paid in BTC. I assume Konsensus has the same stance.
I also spoke with an Estonian author not too long ago, who wrote a book about Bitcoin. He and his podcast co-host / biz partner host their own site where they sell it. The book is also sold in 2 of the largest bookstore chains in Estonia. The chain stores had apparently sold about 100 copies in the first 3 months. Through their own site, there was one order (and that one person was me). Mind you, this is not only about fiat vs BTC as a means of payment, but also about who actually profits - the Estonian bookstores take a 50% cut.