Update: Ask and you receive. Sorta.
I think about textbooks that look like this. The ability to see the whole textbook, all pages at once. The ability to zoom in on videos, that walk you around Delphi or Persepolis or Ur. The ability to look at three-dimensional models of the Parthenon or zoom through the forum of Rome. The ability to link to Wikipedia articles, or definitions of unfamiliar words, or to every word. The ability to link to definitions in multiple languages, not just a Spanish glossary that adds forty pages and extra weight. The ability to hear an audio recording of a section of the Iliad in ancient Greek, while subtitles scroll it to you in six translations (Latin, Italian, Spanish, English, French, Sanskrit — to hear related Indo-European languages). To hear an audio recording of Euclid’s proof of the Pythagorean theorem, while a vector drawing lays out the lines and creates the proof in visual data, and an algebraic formula appears above it. A textbook that allows you to see all the other notes and highlighting left in the book by other students in your class — or in the school district, or in your state, or from your continent, or from the world.
A textbook in which information is updated, but updated with a logged history like a wiki. A textbook in which the editorial changes are transparent, year after year. A textbook that the students help write, like a wiki. A textbook in which an increasing number of images are CreativeCommons licensed, and every photograph of every temple, every fortress, every painting, every portrait, every object, links to its Museum, catalog number, and possibly even website.
Oh, we’re so far from that. At first, they’ll just scan the textbook into pixels, and we’ll view the pages on the iPad or whatever device comes along just like it were a book on the desk.