This article details the results of testing an e-book in two differential calculus classes. Although we, as math instructors, were drawn to the components of the e-book that promote conceptual understanding--such as the interactive figures--the students reported liking the assessment support most. We found that students were initially excited about the interactive figures, but the majority did not use them much over the term. The students who did make use of the interactive figures, however, also reported that the figures improved their understanding of calculus concepts.