In this world, many authors publish exclusively or primarily in electronic format. And many readers say it is their preferred medium for reading books. In fact, in this world, e format is so much the norm that print copies are referred to as Dead Tree Books - or DTBs, for short. The name suggests they are already perceived as quaint ancient artefacts.
Market research in US (currently the hub of e publishing) suggests that in a year's time, twice as many people will own ereaders. So, presumably, twice as many books, whatever their publishing history, will be bought in this form.
In a month's time, kindle is officially launched in UK. It will be interesting to see how quickly we consider our carbon footprints and realise that you don't have to kill a tree to buy a book.