Apple needs to sign some agreements with those who publish college text books. I can't think of any group who (1) buys/reads more books and (2) hates the current state of affairs more than students. This group along could put e-books into the main stream.
The problem with collage text books is that printing and distribution are a very small part of the book cost. It costs quite a bit to write and edit a book (The editing is the hard part). When you publish a work of fiction you can recover the cost over a number of years. Fiction also has a much wider audience to defuse the cost. By the time a text book has hit the presses, it is already painfully out of date. You need to make your money back in one fast printing of a small number of books.
The one exception is 17th century English history books. No changes have happened to 17th century English history since the end of the 17th century.