This paper investigates the use of e-books as learning tools in terms of learner satisfaction, usefulness, behavioral intention, and learning effectiveness. Based on the activity theory approach, this research develops a research model to understand learner attitudes toward e-books in two physical sizes: 10? and 7?. Results suggest that screen size could affect learners' perceived self-efficacy in using 10? and 7? e-books. Interactive learning environments, acceptable screen size, perceived self-regulation, and self-efficacy could positively influence perceived satisfaction with and usefulness of e-books as learning tools. Perceived satisfaction and usefulness are crucial factors in learner behavioral intention which, in turn, contributes to learning effectiveness. The paper also proposes a conceptual research model based on the activity theory approach.