Many e-book readers have become available as e-books are in popular use these days. We first developed the evaluation criteria and elements for testing the usability of e-book readers and then examined the usability of three e-book readers. The usability testing was conducted using three e-book readers that were most popular with 15 participants that consisted of middle school students, university students, and office workers. The study found that iPad showed the best usability. In case of Amazon Kindle, participants indicated that the lack of the touch function imposed a great deal of negative impact on the usability of the interface. Also, the hardware- and software-oriented usability provided by an e-book reader was considered to be a very important element for the users, and the portability in connection with the hardware-oriented aspect of an e-book reader was shown to be of great effect to the overall usability of an e-book reader.