It looks like they've been around since 2010, which surprises me because GitHub was around for a year or two before that iirc. I still envy that username, though!
I always loved downloading them DRM-free. Because it felt like I had actually owned it instead of just reading it from some website that could snatch it back at any second. I know Library Genesis is still up and running fine, but this is a warning of things that could happen.
Also I should probably add (though I'm sure you got this covered), if you make a web client that supports direct messaging, make it work correctly! (unlike Instagram)