Storytelling is an effective way to communicate information to people with different backgrounds and literacy. Immersive technologies like virtual reality (VR) have great potential for presenting engaging narratives and multimodal content in innovative ways. However, it is essential to ensure that the presentation and interaction possibilities are comprehensible to broad audiences. Drawing inspiration from the traditional role of books in preserving stories, we introduce StoryBook, a conceptual metaphor for interacting with and unfolding immersive data stories. Through analogical reasoning, we mapped existing concepts of physical books to interact with a VR storytelling process. StoryBook provides a familiar and intuitive way of navigating, inserting, and extracting story elements in VR, akin to page-flipping, bookmarking, or note-taking with a real book. We developed a prototype and conducted initial user feedback sessions, showcasing the potential of our concepts. Our contribution provides insights into the design and interaction of data-driven stories in immersive environments.