@hailey https://github.com/MiniGlome/Archive.org-Downloader has been hugely beneficial to me. You get FAR higher quality output than the encrypted Adobe PDFs you can decrypt with Calibre tools.
I fear what may now be truly lost due to Archive being forced to hide things. At least a lot of books are 1hr rental so they can be downloaded, but who knows what'll disappear now
And archive has a looooot of books missing from libgen, z-library, and anna's archive.