This book is an introduction to the theory of interacting higher spin gauge fields. It describes in a pedagogical way the methods used, and the results obtained, within the three major approaches to the subject: the Dirac light-front theory, the Fronsdal covariant approach and the Vasiliev AdS theory. Abstract concepts and methods unifying the various appproaches are pointed out. The book follows the ideas behind the first volume; explains the mathematical concepts and tools used, while also reviewing the history of the subject.
