AA compiles from everywhere; LibGen and Z-Lib served as the major sources of books. This has unfortunately led to search results for a particular book containing multiple versions of that book, and it is not readily clear which one is the highest-quality version. A real library would have librarian staff who carefully curate everything, but in the pirate world this isn’t realistic so it just gets all thrown together.

LibGen is now more or less a dead project. The servers of the original version were reportedly seized a couple of years ago already, and other sites under the LibGen name were notorious for piggybacking the original collection and just plastering it with ads. If one wants to upload stuff, better now to upload it to Z-Lib (not a perfect site, but still) and it will then get picked up by AA in a few months.

annas archive is practically a compilation from all sources possible (including libgen afaik)