Anna's Archive (English name Anna's Archive) is a project aimed at categorizing all existing books by aggregating data from various sources, claiming to preserve about 5% of the world's books. The sheer quantity alone is quite astonishing.
This project brings together the content of three globally renowned digital libraries: Z-Library, Library Genesis, and Sci-Hub. It includes a large number of books, papers, comics, magazines, and other resources. It can find e-books on various subjects such as novels, science, history, philosophy, and geography. You can search and download for free using titles, authors, ISBN, etc.
Even relatively obscure authors like Zhou Dedong can find fairly comprehensive resources