The era of e-book came to a step.E-book device is at the center of this era, these e-book device as one represented by kindle imitates paper books. That imitation is the important role of coming the era of e-book?How different books read on computers are from e-book device? Why that books are not generalized? Then, What is interface for optimized reading? This paper start these questions.Recently, Since the advent of various devices such as mobile phones and the tablet pc, reading experiment is done on various devices. The research conclusion that each device is adequate for various interface has came. Of various interface, this paper tries to establish what difference paging and scrolling is in readability each device and what factor causes this difference. Screen size and interaction is assuming factors that cause paging and scrolling in readability. The total eight kinds of text environment was prepared by screen size(Bing vs Tiny) and interaction(Touch vs screen) and Paging and scrolling. The subjects were 24 graduate students, the experimental text was Aesop;;s Fables, and task is requiring a linear reading and comprehension test. Eyetracker is used as a device recording all these experiments. The results is little difference between paging and scrolling in big screen, and paging is higher in readability than scrolling by mouse, scrolling is higher in readability than paging by touchscreen in tiny screen.