The current transition from physical to electronic books opens up opportunities to present semantic information about a book's content. This paper reports on a project that aims to improve the eBook reading experience by presenting semantic information about the eBook content together with the text. The key research challenges included suitable semantic information to be presented alongside a text and manners to display semantic information in an eReader application to supplement the text. We developed a web-based prototype that incorporates analysis of semantic content elements and explored the effectiveness of these semantic elements in a user study with 30 participants. Our results indicate that dynamic semantic visualisations may assist comprehension of existing concepts within an eBook, and provide insight to information that could not be easily gleaned by simply reading the text.