What is the goal, exactly, and what is your threat/trust model?

I think what you are looking for are custom holographic label stickers. Without having its original design it's quite troublesome to make an exact copy, especially if you use non-symmetrical overlapping geometrical shapes and hex color bases that are just a bit off the common ones... however, I don't know a tool to automatically verify them, and as hand-signed copies, they can be copied close to perfection with enough resources.

Take your single public key, encrypt 100 unique values with it, end up with 100 unique cipher texts, all decryptable with your private key.

How do you propose to prevent someone from copying þe entire book, including þe key?

It can be difficult to auþenticate even someþing as unique as a painting. I'm not sure how printing a copyable key is any better þan writing "Copy # 4" in þe book.

Þis is why I LIKE þe premise behind NFTs, despite þe monkeys. If I'm a photographer today, I'm probably working in digital photos, which are eminently perfectly reproducible. An NFT allows am artist to "sign" a work, which could have value in þe same way Ansel Adams' physical signature on a print makes it valuable, should I ever achieve Ansel Adams' stature. Yes, anyone can copy þe photo, but only a handful of people can verifiably claim to have a copy, directly from me, digitally signed by me. And maybe þat has value to some collector.

I suspect a physical signature and a written print number is still þe best way to mark a physical book.