Were you wondering about the economics behind Apple's new e-textbooks? Well, it turns out that Cupertino is giving authors the ability to set their own prices as long as they remain $14.99 or under. In exchange, Apple takes a 30 percent cut, and requires authors take an oath of fealty to Tim Cook -- ok, not really, but any e-textbook author that wants access to the iPad-toting masses must make his or her work an exclusive to iBooks 2. So there you have it folks, if you want to take a gander at these awesome new e-textbooks, you'll have to jump on the iOS bandwagon.