We describe a software book model that emulates a range of properties associated with physical books—analog page turning, visual location cues, bookmarks and annotations—and, furthermore, incorporates many advantages of digital environments—hyperlinks, multimedia, full-text search, automatic identification of synonyms, cross-referencing of key terms with an online encyclopedia, and an automatically generated back-of-the-book index. Usability studies were conducted to compare performance using these books for various reading tasks with HTML, PDF and physical books. Participants completed the tasks more efficiently with the new interface without any loss in accuracy; they also preferred it.