Book excerpt: This is a sceptical history of the internet/stock market boom. John Cassidy argues that what we have just witnessed wasn't simply a stock market bubble; it was a social and cultural phenomenon driven by broad historical forces. Cassidy explains how these forces combined to produce the buying hysteria that drove the prices of loss-making companies into the stratosphere. Much has been made of Alan Greenspan's phrase irrational exuberance, but Cassidy shows that there was nothing irrational about what happened. The people involved - fund managers, stock analysts, journalists and pundits - were simply acting in their own self-interest.