Historically, books and software are very different things. One physical and the other digital. So we think about them as different even though we now call them eBooks and Apps.
Currently the same screen is used for eBooks and Apps. Already, it is sometimes hard to tell the difference just looking at the screen.
But we still talk about the two as very different products. In doing so we leave a gap. There is no reason you could not take the content of an ebook and put it into an app. On the converse a feature of an app would be useful for telling stories in eBooks.