An ebook is represented as a plurality of ebook pages associated with a plurality of segments. A navigation command is received from a user, the navigation command requesting a navigation graphical user interface (GUI) in a particular navigation mode of a plurality of navigation modes. One or more ebook pages, of the plurality of ebook pages, are identified for page thumbnail generation, and page thumbnails are generated for each of the identified one or more ebook pages. The generated page thumbnails are grouped by segment, using the plurality of segments. The navigation GUI is generated in the requested navigation mode using the grouped page thumbnails, the navigation GUI listing at least one segment, of the plurality of segments, and horizontally listing at least one page thumbnail associated with the at least one segment, and the navigation GUI is displayed.