You remember that special education event that Apple held back in January of this year? (It was when they announced the iBooks Author app for Mac and textbooks for the iBookstore, if you didn't know.) Anyway, this was a big move by them and it showed that they want to contribute to education by helping to publish electronic textbooks on iOS devices. While I'm all for this as it's really an amazing idea and all, I think their timing could have been better.
Here's the problem: Apple just unveiled a new iPad with a Retina display that has a resolution of 2048 by 1536 pixels, meaning that all the work publishers put into their beautiful textbooks was nearly all for nothing since many students will be purchasing the new iPad over the older model. (Yes, it would be correct to assume that some students are on a budget, but I assure you that most will desire the latest technology.) Apple should have just saved everyone time and introduced the textbooks after or even alongside the iPad launch.
I mean, there's not a large demand for them now anyway since all the books that have been released are for high school students and everybody knows that most of them use the same book for an entire year, not just one semester like college students -- meaning they won't need a new one until the fall, or the start of the school year. To that end, Apple should have just waited and saved publishers the time of optimizing their graphics for the Retina display when they could have just designed the entire book for the display at the start.