This research examined readers' knowledge of popular genres. Participants wrote short essays on fantasy, science fiction, or romance. The similarities among the essays were measured using latent semantic analysis (LSA) and were then analyzed using multidimensional scaling and cluster analysis. The clusters and scales were interpreted by searching for lexical neighbors in the LSA space. The results indicated that there were 4 main types of essays: those that described science and technology as a theme of science fiction, those that described women and courtship as a theme of romance novels, those that discussed narrative and plot structure, and those that discussed feelings depicted in the text or evoked in the reader. Reading experience with the target genre had little detectable effect on the type of essay written for fantasy and science fiction. A second study demonstrated that even self-selected science fiction fans wrote essays comparable to those written by inexperienced readers. However, reading experience did have an effect on the essays written for the romance genre. In particular, essays written by readers with little reading experience with romance tended to describe the theme and plot structure of romance novels, whereas more experienced readers tended to discuss the emotions of the characters and those evoked in the reader. The results provide evidence about the nature of genre knowledge and the mechanisms for its acquisition. (Contains 6 figures, 9 tables, and 3 footnotes.)