E-readers have a very noticeable delay when flipping through pages, especially quickly. If I'm trying to construct a scheme for preimage collision resistance in

E-readers have a very noticeable delay when flipping through pages, especially quickly. If I'm trying to construct a scheme for preimage collision resistance in my textbook on cryptography (which is a humble 400 page textbook), I'll go to the index first (last couple pages), then flip to the page on preimage resistance, then flip forward 20 pages to collisions in hashes, and then maybe flip back a couple chapters to hash function constructions. That's about 5-10 different pages referenced in quick succession, and an e-reader gives a very significant barrier. Add onto that typing on a e-reader is a pretty awful experience as opposed to scribbling notes in the margins of the textbook and you have a product that doesn't provide any real incentive. One could make the argument that textbooks should be written in a way that accommodates the web and e-readers better, but that's a whole other hill you'll need to climb.