I thought the IA only archives websites and digital contents, which are in danger of being lost? eBooks are seldom the only form of publishing, thus I believe there is always at least an archive copy of them. Making them accessible for all is clearly very controversial.
IA has tons of stuff. Scroll down past the Wayback search on https://archive.org/ to the more advanced search and you can see more categories. You can play a lot of the audio, video, and even some software right in the browser. Their physical archive is also huge. Here are some pictures from 2012 https://scldigital.wordpress.com/internet-archive-gallery/
Oh, I didn't know they even have a physical store! Thanks for pointing out. Yeah, I know they also archived digital audio and other stuffs, but never thought book archiving lies in their realm as well.
