The biggest advantage of ebooks over printed ones is – of course – that there are no more fixed pages. Every device can decide how it wants to display the content. With digital books it is possible to have the same excellent user experience on a small smartphone screen as well as on a huge desktop monitor.
But with all these advantages there also come challenges. One is positioning inside the book. So what to do, when you want to save the user’s current reading position, so that he can continue on the same “page” when he comes back? Since the user can read the text on different devices with different screen resolutions and different text settings (e.g. font size settings) you can not simply save “Page 36″.