Electronic devices which do more than one thing are very popular today. Phones with cameras, web browsers, satellite navigation, games etc. - would have been thought of a science fiction just a few short years ago. Now they are everywhere. On the other hand, there is still a place for devices which do one main job - the key thing for such specialised pieces of kit these days is that if they are going to be single function then they have to be exceptionally good at that one task. The amazon kindle is a perfect example. Its primary function is reading books and, because it uses an e-ink technology display, it fulfils that requirement much better than a computer or a mobile phone.