Consider how to model the book reader's state (e.g., current page, user preferences) and operations (e.g., turning pages, searching) using object-oriented design principles.

Explore data structures that can efficiently handle dynamic page navigation and user interactions, such as a doubly-linked list for page traversal or a hash map for quick access to specific pages.

Design a scalable architecture that separates concerns between the book content, user session management, and UI rendering, while ensuring thread safety for concurrent access in a multi-user environment.