How did an obscure Sheffield band, the Arctic Monkeys, achieve two chart-toppers without record companies or distribution deals? How did one man spark a mass movement by placing an ad in Loot magazine inviting people to "join me"—in what, he didn't say, but he received 4,000 applications. Why do the British now habitually place bunches of flowers at the site of road accidents?

This rather formless book sets out to unravel the mystery previously tackled by two best-selling studies of mass decision-making, The Tipping Point and The Wisdom of Crowds. The first examined how a build-up of buying or voting decisions becomes unstoppable, while the second analysed how a large group of ordinary people is usually better at solving a problem than a small group of experts.

After 330 rambling pages of psychology, anthropology, pop music, and marketing case studies, Earls's conclusion is stunningly obvious. Despite our belief in individualism, we are social animals and our behaviour in the mass-good or bad-is caused by our interaction with each other.

How businesses can influence this mass of potential customers is the apparent purpose of the book, but apart from word-of-mouth, Earls has little else to suggest.