If you own an e-reader you often can only buy e-books from the bookstore that is bundled on your device. Many of the budget e-readers out there don’t even have a bookstore that is accessible by users and many people are left to fend for themselves to load content on it.
Here is a comprehensive free e-book resource catalog online. All of these books are hardware agnostic, which means they are not locked by DRM (Digital Rights Management). All you have to do is simply download a title and load in via the USB cable from your computer to your e-reader. Many of these sites also provide the books in more than one format, so they will work with your Amazon Kindle, Kobo, Barnes and Noble Nook, Sony e-reader and hundreds of others.
Source: goodereader.com