A computer program that functions as an interactive "book" by augmenting text with maps (and possibly other info).
I was reading Plutarch's Lives and had to constantly refer back to the map at the beginning of the book to even have a clue of the spatiality of the conflicts described. Worse yet, there were no maps for the battles, like the famous naval battle of Salamis where the Greeks repelled the Persians.
Imagine a computer program (or web site I guess), with text on the left side (directly from a book) and maps / info on the right. As the user advances from paragraph to paragraph, the map changes, updated with information from the text. Needless to say the data cannot be automatically gleaned from the text, it would have to be finely crafted by a human that understood the text perfectly.
The ideal use case is a description of a battle, in which formations of soldiers would move on the map as you are reading about their maneuvers.