alt Hacker NewsThe articles I've read on this are not clear, but I strongly suspect "rare" is not the definition you and I probably use for the level of rarity of books actually being destroyed.
These are not going to be the kinds of books "The Ninth Gate" resolved around - truly one of a kind. It's not good they are destroying books, but they are books which do have other copies. Just perhaps not many.
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I suspect rare here often means out of print or commercially obscure, not unique
There's just a few copies in a single library worldwide which is probably a national or a university library
At this scale, there are no guarantees of anything. There very likely will be unique copies in there. If these were expert archivists a lot of damage could be prevented, but given the malice and indifference of AI companies, there very likely will not be an expert archivist involved, and unique copies will be destroyed unceremoniously.
Also, a lot of these "rare books" are stuff like TV programming magazines from October 1994.
Quite possibly not many, and no copy held in any form by the copyright owner either. Say a few hundred copies of some obscure book from 40 years ago. They probably won't be erased from the face of the earth by the judicious and proportionate actions of, of a few, AI companies? Hmm.