The iBookstore, Google Play, and Project Gutenberg all offer ebooks using the iPhone/iPad's proprietary format (ePub), so long as you download the appropriate file. Apple's own ebook store, iBooks Store, is included. Ways to find free books within the iBooks app sees how to download books in iBooks.
1. Free iBooks
An online library of free iBooks with over 44000+ titles available to download for iPad, Android, iPhone or any mobile device. It's 100% free. freeibooks.com
2. Project Gutenberg
Project Gutenberg also offers a very convenient way to keep up with newly added books. It's a mother of all ebook sites, there are almost 44,000 public domain books in the catalog. www.gutenberg.org
There are more than 25,000 free ebooks on Smashwords, all are DRM-free. You can first pick a category, and then select Free tab to get a list of free titles in your favorite genre. www.smashwords.com
4. Open Library
The site positions itself as "The World's classic literature at your fingertips". There are over 1,000,000 free ebook titles available. In this site, you can borrow, read and add books. www.openlibrary.org
The site offers 29,000 free ebooks, the number of available formats is impressive. Epub included. manybooks.net
The site is an online ebook catalog, it offers a digital source of free eBooks for any taste. You can find almost 30,000 titles – all of them are free. www.digilibraries.com
It's free to browse all eBook and download it to your iPad/iPhone. You can sell your book on this web. www.epubbud.com
The ultimate eBook library.
Tips: Make sure you've downloaded iBooks from the App Store and installed already. If you have not iBooks installed, please go and install it. (iBooks is free in AppStore)
1. Connect your iPhone/iPad with the internet, and then go to Safari.
2. In the navigation bar, link to this web: tuebl.ca (see step 2).
3. In the search bar, type the name of book that you want.
4. Select the book, and then tap Download Epub option.
5. After downloading it, tap "Open in iBooks". You'll see it in your library, and then you can enjoy it.