Many schools and universities are starting to offer e-Textbooks in place of traditional paper textbooks. E-Textbooks are offered via a variety of reader applications, each having its own user interface for page navigating, search, annotation, and highlighting of text. This study investigated the efficacy of two e-Textbook reader applications, Kindle and Inkling, for an Introductory Psychology text. 40 participants completed tasks during a simulated study session for an openbook quiz using one of the applications. The ability to use the e-Textbook to make notes, bookmarks, highlights, and to navigate throughout a chapter were examined along with user satisfaction, perceived workload, engagement, and comprehension. Results showed that use of both applications resulted in similar levels of comprehension of the material as well as satisfaction, perceived workload, and engagement. Participants were less successful and reported the Kindle to be more difficult to find material using the Table of Contents and to find previously highlighted text than Inkling. Turning pages, however, was reported to be more difficult with Inkling than Kindle. Participants were overall positive about the use of the e-Textbook as a study tool stating that information was easier and faster to find than when using a paper textbook. They also preferred its light weight and portability to a traditional book. Details on these findings and user interface design recommendations for e-Textbook reader applications will be discussed.