The Gambebook Reader app is a versatile file viewer that allows users to interact with and navigate through documents. Users can open files on the app, and the pages of the file are displayed using a ViewPager, enabling easy swiping to move between pages. The app provides several features, including the ability to jump to a specific page by entering a page number, returning to the first page of the document, and toggling the visibility of UI elements, such as buttons and linear layouts. It also incorporates animations for a visually appealing user experience. The app loads and renders file pages as images, and users can zoom in and out on pages as needed. Additionally, the current page number is displayed and updated as the user navigates through the document. This app is a handy tool for reading and interacting with documents on mobile devices.