Since the 1900s, researchers have investigated the nature of books aimed at children, their content, language, and illustrations. In addition, researchers have documented young children’s interest in books, the nature of parent-child interactions during shared reading, and what children learn during shared reading. In this chapter, I reflect on the value of thinking theoretically in order to understand the nature of shared reading and its influence in the lives of young children. To do so, I describe three theories of development that proved influential in my research in general, and for the study of shared reading in particular. The theories include general learning theory, Vygotsky’s zone of proximal development, and Bronfenbrenner’s Ecological Systems theory. I argue that thinking theoretically along with a critical evaluation of the extant research are necessary to design impactful studies. Finally, I consider how digital books might change the nature of shared reading itself.