The End of the College Textbook Racket?
Mark J. Perry says it's nigh, citing "the increasing amount of competition for the college textbook market."
One reason the bubble exists to begin with is that while students have to buy books, professors get to decide which books they'll buy -- it's a third-party-payer problem, where the person making the decisions has no incentive to keep costs down. For the bubble to pop, professors will need to decide it's worthwhile to assign cheaper (and presumably at least slightly inferior) alternatives to the major textbooks. Maybe student pressure can create this outcome.
Here's a nice graph from Perry: