Constructionist principles provide fertile ground for developing innovative approaches to learning. Using a grounded theory qualitative research design, we analyzed participant reports of their experience in an online course in which they collaboratively authored a book. Our qualitative analysis suggested that participants experienced extraordinary engagement and motivation, which they interpreted as being related to the collaborative process, their own agency in the project, and the externalized value of creating an artifact intended for a public audience. A new metaphor for learning emerged from the study based on the concept of authorship. Our authorship learning construct sees learning as a process of authoring understanding and skills while simultaneously authoring at multiple levels of agency, including authorship of processes, roles, goals, artifacts, meaning, self, group identity, and society.