I'd pay at least five dollars and at most 25 for an app that had Leonardo's Notebooks that included all text and pictures. Thered be an interface like the many bible apps. Choose the category ( for example like flight of birds part 1) and itll go right there. Make foot notes and highlight text. Book mark certain parts to go back to later. Mostly i just thought of this because im doing a three page essay on him and have started reading some of the books which appealed to me. Anyone else?