In the seventeenth century, Japanese popular prose flourished as waves of newly literate readers gained access to the printed word. Commercial publishers released vast numbers of titles in response to readers' hunger for books that promised them potent knowledge. However, traditional literary histories of this period position the writings of Ihara Saikaku at center stage, largely neglecting the breadth of popular prose. In the first comprehensive study of the birth of Japanese commercial publishing, Laura Moretti investigates the vibrant world of vernacular popular literature. She marshals new data on the magnitude of the seventeenth-century publishing business and highlights the diversity and porosity of its publishing genres. Moretti explores how booksellers sparked interest among readers across the spectrum of literacies and demonstrates how they tantalized consumers with vital ethical, religious, societal, and interpersonal knowledge. She recasts books as tools for knowledge making, arguing that popular prose engaged its audience cognitively as well as aesthetically and emotionally to satisfy a burgeoning curiosity about the world. Crucially, Moretti shows, readers experienced entertainment within the didactic, finding pleasure in the profit gained from acquiring knowledge by interacting with transformative literature. Drawing on a rich variety of archival materials to present a vivid portrait of seventeenth-century Japanese publishing, Pleasure in Profit also speaks to broader conversations about the category of the literary by offering a new view of popular prose that celebrates plurality.