What might it mean to use books rather than read them? This work examines the relationship between book use and forms of thought and theory in the early modern period. Drawing on legal, medical, religious, scientific and literary texts, and on how-to books on topics ranging from cooking, praying, and memorizing to socializing, surveying, and traveling, Bradin Cormack and Carla Mazzio explore how early books defined the conditions of their own use and in so doing imagined the social and theoretical significance of that use. The volume addresses the material dimensions of the book in terms of the knowledge systems that informed them, looking not only to printed features such as title pages, tables, indexes and illustrations but also to the marginalia and other marks of use that actual readers and users left in and on their books. The authors argue that when books reflect on the uses they anticipate or ask of their readers, they tend to theorize their own forms. Book Use, Book Theory offers a fascinating approach to the history of the book and the history of theory as it emerged from textual practice.