A systematic study of information dynamics that extends beyond what is found in standard logic textbooks. Everything we do is driven by information, but the dynamic process of acquiring information and adjusting our views based on it has seldom been put at the center place in logic, and there are few textbooks introducing readers to this line of work. The present book introduces the reader to major logical techniques for studying information dynamics and interaction between agents, based on a variety of intuitive scenarios as well as recent research. Readers will learn styles of modeling, as well as the basic features of the new logical systems emanating from this line of work. All the separate strands in the book are brought together in a comprehensive study of information flow and action in games, forming a logic-based complement to standard perspectives in game theory.