It's a good question. This site, https://copyrightalliance.org/education/copyright-law-explained/limitations-on-a-copyright-owners-rights/backup-copyright-exce

It's a good question. This site, https://copyrightalliance.org/education/copyright-law-explained/limitations-on-a-copyright-owners-rights/backup-copyright-exceptions/ https://copyrightalliance.org/education/copyright-law-explai..., states "It is important to note that this exception for backup copies only applies to computer programs and not to other copyrighted works, such as digital movies, music, or photographs or ebooks." But it seems unbelievable to me that they would have spent millions copying all these books and not have backups.