Book excerpt: Agent-centric theories, approaches and technologies are contributing to enrich interactions between users and computers. This book aims at highlighting the influence of the agency perspective in Human-Computer Interaction through a careful selection of research contributions. Split into five sections; Users as Agents, Agents and Accessibility, Agents and Interactions, Agent-centric Paradigms and Approaches, and Collective Agents, the book covers a wealth of novel, original and fully updated material, offering: To provide a coherent, in depth, and timely material on the agency perspective in HCI To offer an authoritative treatment of the subject matter presented by carefully selected authors To offer a balanced and broad coverage of the subject area, including, human, organizational, social, as well as technological concerns. ü To offer a hands-on-experience by covering representative case studies and offering essential design guidelines The book will appeal to a broad audience of researchers and professionals associated to software engineering, interface design, accessibility, as well as agent-based interaction paradigms and technology.