If the author voluntarily submits the text, it wouldn't be a problem imo. You could then/also require that any quote over 1 sentence (which could be safely cov

If the author voluntarily submits the text, it wouldn't be a problem imo. You could then/also require that any quote over 1 sentence (which could be safely covered by fair use) or maybe even any quote at all is simply a reference to the book itself- maybe even formalize the referencing system. If they are not copying the text, there is no copyright problem. Copyrights do not act like trade secrets or patents.