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, since 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.
An e-reader is a device designed as a convenient way to read e-books. It is similar in form factor to a tablet computer, but features electronic paper rather than an LCD screen. This yields much longer battery life —the battery can last for several weeks— and better readability, similar to that of paper even in sunlight. Drawbacks of this kind of display include a slow refresh rate and (usually) a grayscale-only display, which makes it unsuitable for sophisticated interactive applications as those found on tablets. The absence of such apps may be perceived as an advantage, as the user may more easily focus on reading.

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