Readmill
Just because you've already gotten your hands on one of the many great e-readers available doesn't mean you should discount the portable reader you have in your pocket at any given time — your smartphone. Readmill ($Free) gives you the kind of reading experience you've always wanted, with the convenience of a device you're already carrying. The app is designed beautifully, paying careful attention to typography, contrast, and usability, and includes a host of adjustable attributes like font size and brightness. The ability to highlight and share your favorite passages makes reading a bit more social, while a wealth of free reading material means you'll never be left without a good book to dive into.