Tina Rosenberg has produced a fascinating insight into groups and the influence of peer pressure. Through a series of case studies, she ably demonstrates the case for using group power to change communities and neighbourhoods and thus the world. From problems as serious as AIDS, alcoholism and recidivism to loneliness and weight loss, groups can solve the problems created by the decline in community that the modern age has brought, and can be used to change both personal and political behaviour. There is value for personal wellbeing in belonging to a community and that too is a worthy goal. This is a fascinating, readable and convincing book that would interest a wide audience.