This book was written for students and practitioners of engineering and social sciences, including computer, information, communication, library, business, management, and cognitive science. The topic is the relationship between people and interactive media. The book describes individuals, groups, and organizations. An understanding of people is critical to an understanding of the technology which can help people. This book was written with the help of a special computer system for authoring called the Many Using and Creating Hypertext (MUCH) system. Students and researchers from the University of Liverpool contributed to the book through the MUCH system. Classes at the University of Liverpool, both undergraduate classes and master's degree classes, have used various drafts of this book as required reading. The book has been available to the students online via the MUCH system, and the students have provided helpful feedback for the contents of the book. The author is particularly grateful for the contributions of Antonios Michailidis and Alex Birchall. Antonios's influence is most prominent in the chapters on groups, and Alex's, in the latter chapters on organizations. Claude Ghaoui coordinated the book authoring and production team, and Anthony Deakin provided finishing touches.