List of 15 sites where you can download millions of books for free.

1. Google Books
2. OpenCulture
3. LibGen
4. Internet Archive
5. Subbook
6. ManyBooks
7. OpenLibrary
8. Good Reads
9. Free-ebooks
10. Bookboon
11. PDFBooks World
12. Obooko
13. O'Reilly
14. E-BookLobby
15. Project Gutenberg