The switch to digital textbooks is happening much faster now. I was checking on the GIS text that I use in my spring class. The author, Paul Bolstad, is now offering an ebook edition of his GIS Fundamentals book. It's offered at a significant discount to the printed, which isn't that expensive as far as books go. Click here to see the book's page.
My alumni magazine from the University of Maine had an article about two professors (sociology and german) who are writing books for flat world knowledge. Students can read the book for free online, buy chapters in pdf, or buy the whole book in a print on demand format.
I'm still not totally on board with ebooks, especially for something like a textbook. But if digital screens get better I can see that they will become the default means for publishing. This will certainly be true if traditional publishers keep jacking up the price by the usual means!