As people spend increasing proportions of their daily lives using social media, such as Twitter and Facebook, they are being invited to support myriad political causes by sharing, liking, endorsing, or downloading. Chain reactions caused by these tiny acts of participation form a growing part of collective action today, from neighborhood campaigns "In this comprehensive masterpiece on social media and collective action, Margetts, Hale, Yasseri (University of Oxford) and John (University College London) set out to rigorously analyze the effect that information provided by or presented to other people has on any one individual, and how cumulative 'tiny acts' of political participation scale up to form, or not form, a mobilization. . . . A compelling read."---Edwin Njonguo, International Journal on World Peace