1. One or more computer storage media devices having stored thereon multiple instructions that, when executed by one or more processors of a device, cause the one or more processors to: display, in each of two display areas, different pages of a digital book using a book display model; display, in response to a request to semantically zoom out, the digital book in a broader context, the broader context using a context display model rather than the book display model; display, in response to a request to semantically zoom in, the digital book in the book display model rather than the context display model; receive a request to enter a scratchpad mode, and in response to the request: automatically combine the different pages of the digital book displayed in each of the two display areas for display in a first of the two display areas and clear at least a portion of a second of the two display areas; display, in the first of the two display areas, the combined different pages of the digital book that were previously displayed in both of the two display areas; and display, in the second of the two display areas, a collection of pages of the digital book that have been moved by a user of the device from the first of the two display areas to the second of the two display areas.