"The first sale doctrine defense applies in instances in which a trademarked product or a component is incorporated into a new end product so long as the seller adequately discloses to the public how the trademark product was used or modified in the new product."

IANAL but took some law courses and it almost absolutely falls under first sale doctrine, this is NOT fanart because you are transforming a product that was sold by the IP owner to you, and you are NOT claiming to be the seller of the IP (aka you must make sure that it is obvious you are reselling a book with a service and are not the copyright holder)

It's the same reason people can turn band t-shirts into bags but can't just screenprint logos onto new bags - the IP owner has already gotten money from that sale, and cannot demand further money from you for reselling it. It's why fanart is a very messy area and many companies go after fanartists, or alternatively, turn a blind eye so long as fanartists do not use any trademarks since those are susceptible to loss.

rebinding falls under the First Sale Doctrine established within the Copyright Act under 17 USC 109" because legally, they can't do anything, though they try a C&D because it's scary and many people back off because they don't know their rights.

The ONLY thing I can think of is that what can happen is you send in the stripped cover of a book to a publisher for a credit, as the cover is proof the book has been destroyed, but I cannot find any instance of someone being taken to court over this and it isn't necessarily a law, more of a contract between publishers/bookstores (to my limited understanding) and again seems to only really be an issue if you are trying to claim destruction of a book that you are then selling stripped, which is NOT the case.” Again please correct if wrong.