I have noticed a sort of change in the terms used for ebooks lately. As recently as a year ago, in all the various publicity that I get regularly from publishers of ebooks, they always used the term ebook to describe their literary efforts, but this is no longer always the case.
A sort of separation between straightforward ebooks (novels and similar) and what we used to call “enhanced” ebooks seems to be happening, which can be confusing. Now, when a publisher or writer sends me details of their latest highly enhanced ebook, they refer to it as an App, especially those who are aiming their work at iPad owners.
In one sense I suppose they are correct in using the term App instead of enhanced ebook, well perhaps two senses, as App is much shorter than enhanced ebook, and in this age of sound bites, abbreviations, Twitting and so on, brevity is a highly valued survival attribute – sadly in my view.