Fast and Slow: Methods for Timely HCI and Interaction Design Research explores the dynamic interplay between rapid and reflective, or long-term vs. short-term research in human-computer interaction (HCI) and interaction design research. In an era where fast approaches to technical research are foregrounded, this book provides a critical examination of the temporalities at play in various research approaches - from long-term empirical studies to rapid prototyping. Ultimately, it asks the fundamental question of how to make timely research contributions and how to plan research projects to be timely in terms of impact. Drawing inspiration from fast and slow thinking, design thinking, and our ever-changing world, this book contrasts "fast" approaches - such as "quick-and-dirty" ethnography, prototyping, and AI-driven automation - with “slow” methodologies that emphasize ethnographic studies, longitudinal research, and participatory design. By working across the fast and slow approaches to research, the book helps researchers and practitioners navigate the trade-offs between efficiency and depth, rapid results, and reflection. Ultimately, the focus of the book is on timely research contributions. With a focus on research approaches, this book presents cases, methodological insights, and theoretical discussions that foreground the temporalities at play in HCI and interaction design research. It questions whether the rush to develop, iterate, and deploy can sometimes obscure critical insights about human behavior, emerging phenomena, ethical considerations, and long-term impact. Whether you are an HCI researcher, UX practitioner, or technology strategist, Fast and Slow: Methods for Timely HCI and Interaction Design Research offers a fresh perspective on how to plan and carry out HCI and interaction design research - over time.