Thanks for the share.
I also like freebookspot.es and avxhome.se.
You don't need to sign up in order to search or download, since the search results points to ebooks uploaded to file hosting sites.
But so far the site with most ebooks is ebooks.wtf.
You must have an account, and be willing to pay a small fee (in BTC) for downloading, but they have a lot of rare academic/historical/political books you don't find in bookstores.
I am beginning to upload my academic collections which are very big.