The following images show how to implement interactivity on epub books. This example is illustrated with some pages from children’s classic picture book Where the Wild Things Are, by Maurice Sendak.
When the reader tap on any word from the text, the associated image of the page will fade in as a popup. Tap on the image again to dismiss it.
If instead of tapping on the image, you double-tap, the image is shown in full screen. With a new double-tap, it returns back to text.
And now, showtime…
I have added a very nice video of the book, found on Youtube, to the epub file. Video works on iBooks on iPad and the outcome is really, really cool.