No, I do not think it would be a derivative work, at least not in the way the term is normally used.
For an anology, consider MS Word. When I create a document using MS Word and save it in one of Words native formats, this file includes all sorts of information generated by MS code and includes MS specific formatting information. That does not, in any traditional meaning of the word, mean that my essay is a derivative work of MS Word.
Many of the people who have created GPL (not LGPL) libraries would disagree. Strongly.
These files don't just contain "formatting information". They contain actual executable code created by Apple. Apple's claim lies on the distribution of their code, not your content per se. They can put any restrictions on the distribution of their code that they want, whether we like it or not (and I don't particularly like it myself). They're not claiming ownership of your essay. They're claiming ownership over the code they wrote, which their system uses to display it. Not the same thing.
What you, and others, are claiming is that this type of license has no legal effect. That's clearly wrong.
Let's not confuse the two issues of whether it's a good idea for Apple to do this (it isn't) and whether they're legally allowed to do it (they clearly are).
However, these textbooks are more than just formatted text. They're interactive; they are essentially a specialized website of sorts. You can include your own HTML and JS based 'widgets' and presumably use Apple's HTML/JS based widgets. The inclusion of Apple source code embedded in the book I believe would technically make the book a derivative in the way the term is normally used.
Whether I personally believe in my gut if it is right that these books be deemed derivatives is a separate issue.. ;)