This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read on the Oxford Academic platform and offered as a free PDF download from OUP and selected open access locations. Aimed at undergraduate students in computer science, design, and engineering programs, and master students in dedicated programs, this is the first comprehensive textbook for students of human-computer interaction. While HCI is primarily a research-driven field, the book focuses not only on scientific principles of interaction, but also on the very concrete goal of designing better computing systems. The book revises and synthesizes topics that have been previously scattered across multiple books and papers, including design, engineering, empirical methods, and technology. Although it covers emerging topics like VR and AI, the book places its emphasis on the more time-enduring principles and methods. The book is open access and comes with associated materials for teachers and students, available on the book's companion website. Kasper Hornbæk, Professor of Computer Science, University of Copenhagen ,Per Ola Kristensson, Professor of Interactive Systems Engineering, University of Cambridge ,Antti Oulasvirta, Professor of User Interfaces, Aalto University Kasper Hornbæk is a Professor of Computer Science at the University of Copenhagen. His core research interests are in human-computer interaction, theories of interaction, user experience, and extended reality. Per Ola Kristensson is a Professor of Interactive Systems Engineering in the Department of Engineering at the University of Cambridge and a Fellow of Trinity College, Cambridge. He leads the Intelligent Interactive Systems group, which belongs to the Engineering Design Centre. He is also a co-founder and co-director of the Centre for Human-Inspired Artificial Intelligence at the University of Cambridge. Antti Oulasvirta is a Professor of User Interfaces in the Department of Information and Communications Engineering at Aalto University. He leads the Computational Behaviour Lab. He is a computational cognitive scientist with an interest in predictive models of human performance in interactive computing.