Textbooks are obviously open to the same digitization and free-access issues as other media, but their sales model fundamentally different because it's one giant principal-agent problem.

In public schools, digitization won't touch textbook profits any time soon because they're bought in bulk, and because multi-year use keeps costs reasonable. Giving out digital copies isn't a major edge if you can get 5-10 years out of a book. As for college students, there's just very little incentive to care about costs. Example: for many of my classes, buying and reselling textbooks, renting them, and getting digital-only access mysteriously converged on the same price - just like you'd predict in a market with no real competition. So the only real question is whether sellers can control piracy or other covert cost reductions like buying international versions and older editions.

So far, they seem to be doing pretty well at it. Altering problems in foreign and new additions doesn't stop everyone, but it deters many students. Mandatory online courseware with in-book CD keys is a masterstroke, since it not only kills piracy but forces students to buy $100 books they might have forgone altogether - no more using library copies if you're hard up for money!

I've only seen two hints of change. One is outreach to agents (i.e. professors) on quality; there are now mix-and-match services that will sell combined chapters from a variety of books, which might someday drive more competition among writers and professor awareness of book choice. The second is the existence of student rebellion in specific majors (i.e. Computer Science) where students are very likely to have digital, pirated, or nonexistent textbooks, to the point where things like "open book exams" are considered outrageous.