This study examines the motivation behind heavy book usage, which is a rarely researched form of extreme media usage. In this study, we develop an explanatory model for the phenomenon of heavy book usage by focusing not only on the immediate gratification of needs through the reading of a book (e.g., entertainment) but also on the motivation to use books for symbolic communication in social interaction. As a result, our model of heavy book usage includes several social benefits that are offered by books including the opportunity to express one’s identity through the visible possession of books. To test this model, 613 heavy book users in Germany with varying sociodemographic backgrounds participated in online and offline surveys. Two multiple regression models show that both reading at a heavy level and the possession of large numbers of books can be explained by the need to express oneself in symbolic communication, whereas the motivation to gratify needs such as entertainment or relaxation does not lend itself to this explanation. A cluster analysis including personality traits indicates that different types of heavy book user use distinct patterns of communication via books. The results imply that book usage is more than simply spending time in the individual activity of reading; rather, books can help heavy book users to express their identity in social interaction.