A month ago by the author himself.
<a href="https://news.ycombinator.com/item?id=6533997" rel="nofollow">https://news.ycombinator.com/item?id=6533997</a>
Most of these books are not PDF, but if you own PDF books, here is something you can try to organize/search them: <a href="https://register.blib.us" rel="nofollow">https://register.blib.us</a> (and access them from anywhere)