If you have picked up this book and are browsing the Preface, you may well be asking yourself"What makes this book different from the large number I can find on amazon. com?". Well, the answer is a blend of the academic and the practical, and views of the subject you won't get from anybody else: how psychology and linguistics influence the field of requirements engineering (RE). The title might seem to be a bit of a conundrum; after all, surely requirements come from people so all requirements should be user-centred. Sadly, that is not always so; many system disasters have been caused simply because requirements engineering was not user-centred or, worse still, was not practised at all. So this book is about putting the people back into com­ puting, although not simply from the HCI (human-computer interaction) sense; instead, the focus is on how to understand what people want and then build appropriate computer systems.