Researchers have pointed out that interactive e-books have rich content and interactive features which can promote students' learning interest. However, researchers have also indicated the need to integrate effective learning supports or tools to help students organize what they have learned so as to increase their learning performance, in particular, for abstract and complex learning content such as that in law courses. In this study, a concept-mapping-based interactive e-book learning mode was proposed. To understand the learning effects, a quasi-experimental design was used to compare the learning achievement and motivation of the students learning with the proposed approach (experimental group) and those learning with conventional interactive e-books (control group) in a junior high school fundamental law course. Meanwhile, the learning achievement and motivation of the students with different learning styles were also explored. The experimental results showed that the proposed approach significantly improved the students' learning achievement, especially for the active-style students; moreover, it was found that the lead-in of concept mapping did not affect the students' learning motivation. Factors that might affect the students' learning achievement and motivation with the concept-mapping-based interactive e-book approach are discussed accordingly.