I have a vision that text books should use a "google map style" to present content. Because when I am reading something new in a branch of knowledge I am not familiar with I always find myself lost (where am I?) in the middle of the book forgetting where what I am reading right now belongs in the overall context. Maybe this is just how my brain works but I think that is common. So I would love to mouse wheel to zoom out and check where exactly I am. So the "street view" would be like opening the pdf file itself and read it normally. Instead of page up and down (like in a normal book) we should navigate like in a map (with several levels like street, neighborhood, cities, states, country etc). Of course we can think of features like the location size relating to how many pages are under that level, marking "places" you have already read, pre-requirements to understand some text could be seen as visa and so on. The author of a book instead of making a simple table of contents would make a map (in fact any reader would be able to make his interpretation of the book and create a map other user could use). I can elaborate more.
There a lot of good programmers here and may someone is looking for a good idea. I don't want anything, but I know I can't make a program bigger than 1000 lines. I have read hundred of textbooks and I am convinced that is that way things should be, we are too attached to physical book even in the electronic media versions. I tried to find something like this but couldn't find. The closest thing I found was Prezi but that is for a totaly different purpose. I think a decent implementation could attract Amazon interest. I imagine a community per book were people create maps for that book or at least one map together. Making a map would be a great exercise to fix concepts and specially contextualization than just reading from page 1 to 500.
I like to discuss things for the sake of discussing things so if anyone wants to share they thoughts I would appreciate. I would be proud if anyone become a millionaire from an idea I had but was to lazy to make it happen.