As the progress of computer technology, an e-book will play an important role at the age of digital learning. It is certain that the user interface design and interaction styles of an e-book will have an important impact on the usability. Nonetheless, currently only few research studies pertinent to the user interface design of e-books are available. The purpose of this research is to explore the user interface design of multimedia encyclopedia. Several multimedia encyclopedias available on the market were collected and tested for their interface usability. In addition, relevant research archives were also investigated to help strengthen the theoretical and practical user interface design issues in this study.

The experiment in this research was divided into two stages. At the first stage, the published multimedia encyclopedias on the market were collected and analyzed. At the second stage, based on the results generated from the previous stage and related archives, the researcher created three prototypes of e-books for further usability testing. The “between-subjects” experimental technique was adopted in this research study. Each participant was required to conduct several interaction tasks according to research hypotheses. After that, they were asked to fill out a System Usability Scale (SUS) questionnaire to obtain their subjective feelings. At the second stage, after the tasks, participants were also needed to fill out a NASA Task Load Index (NASA-TLX) questionnaire to measure their mental and physical loads while conducting the interaction tasks.

At the first stage of experiment, the design of index structure, orientation cues, and bookmark management tool of the published multimedia encyclopedias were the primary research focuses. At the second stage, the main research focuses were the navigating strategy, content style, and bookmark tool. The research result generated at the first stage was: (1) non-hiding index structure, (2) color changeable orientation cue, and (3) fixed bookmark management tool, all provide users with better interaction performance and subjective preferences. At the second stage, the research findings were: (1) providing users with switch key to facilitate their navigation, (2) enable content with “full text” and “outline” mode, and (3) providing intelligent bookmark tool that can remember users’ position can also provide users with better interaction performance and subjective preferences.