If you're in need of ebook content, but you don't want to pay an arm or a leg for it, you'll want to check out TopHQBooks. It's a search engine you can use to find high-quality PDFs that you can download to your ereader or computer.
The selection isn't bad either. There are magazines, books on learning to code, and a variety of other stuff. The selection of fiction appears to be pretty small, but if you're looking to learn something, this appears to be a great reference library -- especially for technical topics.
Each book's page is useful as well. You get a picture of the cover, an easy-to-find download link and descriptive information. You may not always find the book you're looking for, but it's a great resource if you want to pick up some free content. Even if you don't have an ereader, you can just print the PDF out and read it the old-fashioned way.