Backstory: It's been awhile since I've been in college but I overheard someone complaining about "$300" textbooks and it brought back horrible memories of those overpriced books.
The Idea: Ebook version of textbooks subsidized with ads.
Deep Dive: You would convert a textbook in a virtual ebook and place dynamic ads in the "book." The goal is to reduce the overall cost to the student in exchange for advertisements.
Since college students are typically poor, another angle is to target the parents. In exchange for the parents purchasing a cheap "ebook" for their student, they would agree to receive advertiser emails for a year.
Validation: Everyone agrees textbooks are overpriced, this may be a way to help bring down those costs.
Monetization: Ads! This whole idea is one giant advertisement.