Books is a little odd in that Apple stuck to plain, black and white novels instead of showing their full range of text books, picture books, comic books, and more. Apple is still ahead of Amazon and the Kindle when it comes to the power of their books format, and the quality of their visuals, so making that part of the pitch would have made sense. Sticking to novels may give the illusion of catalog and ereader parity with Amazon, but it keeps the fight on Amazon’s terms.
Also, Books and Photos, wisely, keeps things at a distance so it’s hard to see the difference in quality between the Retina iPad 4 and the non-Retina iPad mini. Because of the way the human brain works, Photos are more forgiving of lower resolution than text, but why take chances?
Whether or not that’s a fair representation of the differences between both products is another story.