Over the past twenty years, amateur fanfiction writers have published an astonishing amount of fiction in online repositories. More than 1.5 million enthusiastic fanfiction writers—primarily young people in their teens and twenties—have contributed nearly seven million stories and more than 176 million reviews to a single online site, Fanfiction.net. In this book, Cecilia Aragon and Katie Davis provide an in-depth examination of fanfiction writers and fanfiction repositories, finding that these sites are not shallow agglomerations and regurgitations of pop culture but rather online spaces for sophisticated and informal learning. Through their participation in online fanfiction communities, young people find ways to support and learn from one another. Aragon and Davis term this novel system of interactive advice and instruction , and describe its seven attributes, each of which is supported by an aspect of networked technologies: aggregation, accretion, acceleration, abundance, availability, asynchronicity, and affect. Employing an innovative combination of qualitative and quantitative analyses, they provide an in-depth ethnography, reporting on a nine-month study of three fanfiction sites, and offer a quantitative analysis of lexical diversity in the 61.5 billion words on the Fanfiction.net site. Going beyond fandom, Aragon and Davis consider how distributed mentoring could improve not only other online learning platforms but also formal writing instruction in schools.