An enormous collection of books. It may need to be accessed via Tor, or you can try the alternative sites:
A large collection of free e-books.
A large audiobook collection.
A fast and filterable search engine for PDFs from across the web.
Another large eBook library. Alternatives:
Free IT and computing eBooks.
~35GB of computer science books.
A collection of books from throughout time.
As the name suggests, a collection of audiobooks about history (and some other topics too).
A MEGA archive of books in German.
A Telegram library channel.
A Telegram channel containing books about military tactics.
A Telegram channel containing books about history and politics.
A Telegram discussion group for sharing and archiving books.
A Telegram channel containing German books.
A guide to studying Western philosophy.