Rare, certainly: there are plenty of vanity publications that were chucked into the bin by almost everyone who was unlucky enough to be given a copy. Precious? Well, with the help of an electronic friend I found ISBN 978-3-8365-7349-8. Apparently a copy of that book is worth about £40k. Can anyone beat that?

(EDIT: I'm assuming "precious" means the same as valuable here to make the question easier to answer. In fact, of course, people usually say "precious" when they mean a personal or emotional attachment or cultural importance rather than economic value.)

There are, but, quoting from the article:

> Anthropic said: "None of our data acquisition programmes buy and destroy rare or antiquarian books."

This statement was clearly carefully worded, using the words "rare or antiquarian" to mean "pre-1966, pre-ISBN". Their statement is answering a question that wasn't asked, so that (if they need to) they can claim in the future that they never said they weren't destroying books with ISBNs.

In the lost media sense? I'm not sure.

Of course there are always post 1960 books which are rare and valuable for being very limited run first editions, signed copies etc.