An e-reader, also called an e-book reader or e-book device, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals. Any device that can display text on a screen may act as an e-reader; however, specialized e-reader devices may optimize portability, readability, and battery life for this purpose. Their main advantages over printed books are portability. This is because an e-reader is capable of holding thousands of books while weighing less than one book, and the convenience provided due to add-on features. Wikipedia