Does an equivalent exist on the darknet? They wouldn't be able to take that down, especially if it's built upon decentralisation for the books themselves. The index could be centralised, curated, or built by the community with the ability to back it up.
The internet archive is a great project but it's baffling to me how difficult it is to distribute the content. It's incredibly difficult to go "I have X amount of space available, store some of it on my disk". More advanced stuff like "distribute the top content on my hard drive. I have X amount of space to give and X bandwidth".