Although gender differences are known to exist in the publishing industry and in reader preferences, there is little public systematic data about them. This article uses evidence from the book‐based social website Goodreads to provide a large scale analysis of 50 major English book genres based on author genders. The results show gender differences in authorship in almost all categories and gender differences the level of interest in, and ratings of, books in a minority of categories. Perhaps surprisingly in this context, there is not a clear gender‐based relationship between the success of an author and their prevalence within a genre. The unexpected almost universal authorship gender differences should give new impetus to investigations of the importance of gender in fiction and the success of minority genders in some genres should encourage publishers and librarians to take their work seriously, except perhaps for most male‐authored chick‐lit.