The counterfeit book won't have an NFT. Someone browsing Amazon will buy a counterfeit Jane Friedman book, and won't know to look for an NFT. The only people who know to look for an NFT will be those who read Jane Friedman's website where she talks about her NFT books, and they'll buy a book from a link on her website, so the NFT won't serve a purpose because they'll already be buying a real book from a trusted source.