This is an open access book. Decide Better: Open and Interoperable Local Digital Twins explores the transformative potential of Local Digital Twins (LDTs) in urban governance. The book begins by introducing the concept of LDTs, which create digital replicas of cities or regions, combining real-time data and simulations to inform decision-making. It highlights how LDTs can enhance urban management by fostering collaboration among stakeholders and providing evidence-based insights for policy and operational strategies. The book emphasises the importance of openness, interoperability, and ethical use in LDT development, offering practical guidance for policymakers, urban planners, and technologists. The book is divided into three parts. The first part discusses the foundational principles of LDTs and their role in making cities smarter through data-driven decision-making. The second part focuses on implementing reusable LDT architectures, emphasising standards and interoperability. The final section addresses maximising LDT impact, offering strategies for governance, scalability, and ethical considerations. Drawing from real-world examples and expert insights, the book provides a comprehensive framework for adopting LDTs in diverse urban environments, aiming to advance sustainable and citizen-centric urban development.