This paper is concerned with the development of e-textbooks. We claim that analysis (and design) of e-textbooks requires the development of a specific frame. Digital affordances provide particular opportunities (e.g. in terms of interactions between users) that require specific considerations for their analysis, as teachers and students use them for their individual and collective purposes. In this study, we develop a framework for mathematics e-textbook analysis, based on the notion of "connectivity." We introduce criteria to assess the different aspects of connectivity and build an analysis grid for e-textbooks. We illustrate the framework proposed by analyzing 2 commonly used French grade 10 mathematics e-textbooks. The results of the analyses show that there are major differences between the 2 e-textbooks in terms of connectivity, which can be related to differences in their design. Beyond these 2 examples, we claim that focusing on connectivity is a useful and relevant way of analyzing e-textbooks, as it can provide a window into issues of interactivity, both practically and cognitively.