'While social platforms like Facebook, WhatsApp, LinkedIn and Twitter have a much broader reach, the uniqueness of massively multiplayer online games (MMOGs) and virtual worlds is that the participation in them is deep. Driven by various motivations, including achievement, socialization and immersion, participants can spend multiple hours a day on such platforms - deriving experiential benefits that are far beyond superficial, and often satisfying at a far deeper level. From a social science perspective, this provides a unique opportunity to extend and refine social science theories in a far more nuanced manner than before, and use them to build models for various applications. The key to this has been the availability of fine grained data about behavior, the 'big data of social science', as well as the development of a new social science research methodology which is based on computer science techniques like machine learning and social network analysis. We are witnessing the start of a new era in social science research, and this book is a timely collection of some of the best work in this rapidly expanding area of inquiry.' Jaideep Srivastava, University of Minnesota