An alternative is plain old school irc. I’m not kidding.
Connect to irc.irchighway.net then /j #ebooks then !search <author and/or title>
Receive search results via xdcc which gives you the commands to download that stuff.
Or query one of the bots (e. g. @bsk) and get a list of hundreds of thousands of books that are available and search that for what you want.

I prefer that over ad infested one click hosters with countdowns, link shortener cascades and captchas. I find and get the stuff much faster by using irc.

What is on libgen? Movies? Animes? Songs?