https://ebooks.wtf/
I found this site in the comments while reading up on why Libgen.org went offline, and thought to share the link.
Supposedly it has more books than Libgen and the site was launched by the guy a couple of months ago.
Libgen Goes Down As Legal Pressure Mounts –June 22, 2015
https://archive.is/2U91L
https://torrentfreak.com/libgen-goes-down-as-legal-pressure-mounts-150622/