I should have unpacked my comment but it was late. I agree with mmerriam about the 'how', but there are awkward exceptions. For example, my public library has two book sales every year during which it sells enormous numbers of recently published books. If libraries as lenders of books are exempt, what happens when they sell books? What about thrift shops or charity book sales? I think I know the answer to those questions as well, but what I'm suggesting is that if customers are forced to pay more for second-hand books or if book shops and paperback book exchanges go out of business, those of us who buy mostly used books will find other ways to get them.

Many millions of unsold books are pulped every year. Why should consumers be penalised because the publishing industry is a mess? ^RQ

That's my superscript for Rhetorical Question.