DRM may help, at least for a while. That's the implication of Randall Stross' NYTimes article on evolving business models for college textbooks.
The textbook publishers have abundantly good reasons to promote e-books. When Cengage sells an e-book version of “Organic Chemistry” directly to students, for $109.99, it not only cuts out the middleman but also reduces the supply of used books at the end of the semester.
THE e-book is wrapped with digital rights management, which, history indicates, will be broken sooner or later. But as long as it does work, digital publishing with a subscription model is a much fairer basis for the business. Such an arrangement spreads revenue across multiple semesters, so it isn’t the unfortunate few students in the first semester with a new edition who shoulder the bulk of the burden.