Here are 20 websites where you can download books for free:

Project Gutenberg .com

Open Library .org

Google Books .com

ManyBooks .net

PDF Drive .com

Bookboon .com

Free-Ebooks .net

Smashwords .com

DigiLibraries .com

GetFreeEbooks .com

Obooko .com

Baen Free Library .com

Internet Archive .org

HathiTrust .org

Standard Ebooks .org

ReadPrint .com

Bookrix .com

Librophile .com

Online Books Page .edu