E-books are changing the way we read. They're the only way to fit an entire library in your purse or pocket.

Though they're cheaper than their print counterparts, e-books still cost money. Actually filling your device with these digital wonders could be costly.

Fortunately, these sites offer thousands of e-books at no charge. In addition, all of them offer books in multiple formats. They make it easy to find the one that works for most of your devices.

eBooksRead - This site offers a huge collection of e-books. No matter your favorite genre, you're sure to find something you'll love among the 300,000 books on eBooksRead.

This site also recommends other authors based on your favorites. You'll find pages for similar writers embedded right into the search page for easy navigation.

Feedbooks - When a site has hundreds of thousands of books, it might be hard to find the one you're looking for. Feedbooks has a picture-based search system that makes it easy to find the perfect book for you.