This isn't even movies wherein some large studio's can send notices. I don't think publishing houses have that many funds to send so many legal notices.
That's what people said about music and films too. You don't want to be the next Jammie Thomas.
This is an existential threat to the deep-pocketed likes of Elsevier et al. They will use the law to make an example of anyone too close to their sphere of influence; so if you are in the US or the EU; support the efforts of LibGen vocally and loudly, and contribute anonymously, but don't risk your neck to the extent where they can get a hold of you.
There are plenty of ways to support the effort safely though. Make sure people who wish to access scientific papers and books know where to go, and make sure your elected officials know about the need for publicly funded science to be published free of charge, open access, (retroactively too).
I'm guessing a pretty significant minority of HN's users maintain offshore seed boxes to get other copyrighted content and for them it might be pretty trivial to add partial peering of libgen content.
Books are a safe bet to pirate