In the last few years, open textbook development has picked up dramatically due both to the expense of commercially published textbooks and the increasing availability of high-quality OER alternatives. While this offers a tremendous benefit in terms of lowering student textbook costs, the question remains, to what extent (if any) do open textbooks influence the amount and method in which students engage with their open textbooks. The answers to these questions should provide useful new insights for all involved in open textbooks and aid in their continued development and propagation. Despite seeming difficulty in gathering data to answer these questions, the digital nature of open textbooks, makes it possible to enable a learning analytics system for open textbooks to track how exactly students are interacting with their open textbooks. To date learning analytics for open textbooks has received relatively little attention. To this end, this paper proposes a framework that can act as a useful guide for setting up learning analytics system for open textbooks also applicable to other digital textbooks. The paper concludes by outlining directions for future work.