It is available over IPFS. Do you have a client installed and running?

EDIT: if you do have IPFS and the companion extension then libgen.crypto should resolve to something like `http://libgen.crypto.ipns.localhost:8080/` which currently works as advertised.

It's not a Web-site. It is more suitable to call it antisite since it has no single location where its content is hosted.

To access it, you need to use software given in the description

https://libgen.fun/dweb.html