Books
Library Genesis
An enormous collection of books. It may need to be accessed via Tor, or you can try the alternative sites:
Project Gutenberg
A large collection of free e-books.
AudioBook Bay
A large audiobook collection.
PDF Drive
A fast and filterable search engine for PDFs from across the web.
Booksee
More eBooks.
All IT eBooks
Free IT and computing eBooks.
Gentoomen Library
~35GB of computer science books.
LibriVox
Public-domain audiobooks.
CyberAlexandria
A collection of books from throughout time.
History Audiobooks
As the name suggests, a collection of audiobooks about history (and some other topics too).
German books
A MEGA archive of books in German.
CyberAlexandria
A Telegram library channel.
Kriegsbibliothek
A Telegram channel containing books about military tactics.
La Biblioteca della Favela
A Telegram channel containing books about history and politics.
Doomsday Alexandria
A Telegram discussion group for sharing and archiving books.
Buecherkiste
A Telegram channel containing German books.
/lit/ Guide to Reading Western Philosophy
A guide to studying Western philosophy.