I never heard of the site. But looking at it now, I can't see how it's anything else other than piracy.

I looked up one of my favorite authors ( https://annas-archive.org/search?q=scott+sigler ) and you can download practically his lifetime's worth of work in 5 minutes. This is not some author who lived 200 years ago - he is living and writing books now and this is his livelyhood.