This essay critically examines Sketches by Boz as Charles Dickens's self-conscious representation of the anxieties of authorship, especially in its early stages. At a time when the young, budding writer had launched his public career, hopeful of lasting celebrity and aware of the risks of the literary venture, Dickens's projection of uncertainty in his own particular formation and practice of the sketch sets up the sketch's dynamic relation to nineteenth-century theater and visual culture. “Astonishment,” the essay argues, emerges as a device Dickens borrows from the stage and adapts for the sketch. The many appearances of astonishment in his sketches, not limited to scenes of performance but also extended to depictions of the everyday, reveal his growing consciousness of unpredictability and impermanence in his work's public reception and potential for generating social transformation. In three sections, the essay analyzes the influence of theatrical anxieties and styles on the form and content of Sketches, locates the theatrical affect of astonishment in everyday contexts, and explores astonishment's capacity for activating social reform.