The use of e-book readers (e-readers or electronic-readers) has become increasingly widespread. An e-reader should meet two important requirements: adequate legibility and good usability. In our study, we investigated these two requirements of e-reader design. Within the framework of a multifunctional approach, we combined eye tracking with other usability testing methods. We tested five electronic reading devices and one classic paper book. The results suggested that e-readers with e-ink technology provided legibility that was comparable to classic paper books. However, our study also showed that the current e-reader generation has large deficits with respect to usability. Users were unable to use e-readers intuitively and without problems. We found significant differences between the different brands of e-book readers. Interestingly, we found dissociations between objective eye-tracking data and subjective user data, stressing the importance of multimethod approaches.