There is another bigger one: College Book Industry.

The current system is pretty inefficient. This probably differs from country to country. The current system here works like this:

The universities give lists of subjects and prescribed textbooks to brick-and-mortar bookstores. They then buy the books and sell them at a huge mark-up.

Students generally do not order online because of the time delay/import BS and many do not have a fixed postal address. Secondhand book sales are a bit of mess because it is not centralised, etc...

There are possibly quite a few ideas on how to make this system more effective (esp. in countries in which the internet penetration is not that high but the cellphone penetration is).