1. Project Gutenberg

Project Gutenberg offers more than 57,000 free eBooks from the public domain. It is free to read and redistribute. There are no fees, and no custom apps are required. You won’t find the latest bestsellers on Project Gutenberg, but you’ll find plenty of great classic books available 24/7 at no cost.
2. Open Library
Open Library is a non-profit Internet Archive that is open and has an editable library catalog.
3. Google eBookstore
Google eBookstore has an option to access free books from the huge collection that features hundreds of classics and contemporary bestsellers.
4. Amazon Free Kindle Books
Amazon Free Kindle Books offers top free books for download.
5. Internet Archive
Internet Archive offers more than 15,000,000 freely downloadable books and texts. They also encourage our global community to contribute physical items, as well as upload digital materials directly to the Internet Archive.
6. ManyBooks
ManyBooks can read on most of the reading platforms like eReaders, Kindle, iPads, and Nooks.
7. BookBoon

BookBoon is the world’s largest publisher of online educational literature. They offer over 1000 free eBooks for you to download.
8. LibGen/Library Genesis
LibGen is a search engine that helps you download books and articles related to science.
9. FreeBookSpot
FreeBookSpot offers lots of links to free ebooks in more than 90 categories. It is where you can find and download free books.
10. Free eBooks
Free eBooks offers thousands of free eBooks to use anywhere you want. They feature some of the best categories such as Fiction, Nonfiction, Romance, Sci-Fi, Self-help, and Business.