The Smart Sustainability Transformation Playbook aims to demystify the socio-technical systems and processes of sustainability transitions through the study of 12 smart cities -- Auckland, Boston, Copenhagen, Gothenburg, Guangzhou, Hangzhou, Medellin, Melbourne, Milan, Seoul, Tokyo, and Vancouver, selected from the IMD-SUTD 2021 Smart City Index. The selection encompasses a range of smart cities and developments on selected critical areas in economic prosperity, social inclusion, and environmental sustainability. The analysis draws on literature review, secondary data, interviews with city officials, and case studies of smart city projects in the 12 cities to better understand how people, organisations, and technologies interact to achieve the city's smart vision for sustainability. Attention is pivoted towards clarifying the characteristics and conditions that help smart cities formulate their visions and strategies on selected issues of economic prosperity, social inclusion, and environmental sustainability; unpacking the processes and outcomes of smart city innovations and transformations with case examples; developing a checklist of critical success factors and pitfalls when implementing smart city innovations; and consolidating a micro-foundation of good practices on success factors and pitfalls in smart city development for long-term change.