Article is not available without registering. As for the title, "destructive" book scanning means you cut off the binding and put the pages in a scanner which easily flips through them and takes the pictures. If you're not scanning rare old books, this is a perfectly reasonable way to do it, because setting up a scanner for a normal book and manually turning each page to scan it takes a long time (Internet Archive has videos on how they do it, very nice and impressive, and logical since their original mission was scanning old public domain stuff, i.e. published before 1930 or so). If Anthropic will actually legally buy all those thousands upon thousands of books, that will be a pleasant precedent for an AI company.

Although I very much doubt that random uncritically gathered textual material can "teach their AI tool how to write well". They're still pushing for more and more training data, even though it's clear actual advancement will have to happen (if it can happen) through more refined usage of / training on the data.