Libgen is FUCKING DEAD
Right now it seems like the best book site is AA

https://en.wikipedia.org/wiki/Anna%27s_Archive
https://old.reddit.com/r/Annas_Archive/
https://annas-archive.gl/
https://annas-archive.pk/
https://annas-archive.gd/
Don't recommend using non-official links since they're likely honeypots/malicious