Robert Darnton divulges his fantasy in Publishers Weekly.
I want to write an electronic book. Here is how my fantasy takes shape. An “e-book,” unlike a printed codex, can contain many layers arranged in the shape of a pyramid. Readers can download the text and skim the topmost layer, which will be written like an ordinary monograph. If it satisfies them, they can print it out, bind it (binding machines can now be attached to computers and printers), and study it at their convenience in the form of a custom-made paperback. If they come upon something that especially interests them, they can click down a layer to a supplementary essay or appendix. They can continue deeper through the book, through bodies of documents, bibliography, historiography, iconography, background music, everything I can provide to give the fullest possible understanding of my subject. In the end, they will make the subject theirs, because they will find their own paths through it, reading horizontally, vertically, or diagonally, wherever the electronic links may lead.
Doesn’t that sound like a Choose Your Own Adventure book? But instead of choosing which way the story goes, you choose how deeply to investigate the story. Start with a fictional sentence, branch into paragraphs of backstory and exposition, link to photos and objects from the characters’ world, devolve into Merriam-Webster definitions and Wikipedia entries.
Brilliant. Who’s writing it?