This book aims to take stock of REDD+ progress, point to critical issues, and suggest how to move forward so that REDD+ and other, newer climate mitigation initiatives are effective, efficient and equitable. We aim to be constructive critics: critical, because the world cannot afford projects and policies that do not help reduce emissions; and constructive, because if the world fails to reduce emissions from deforestation and forest degradation it is unlikely to stay below the 1.5°C (or even 2°C) target. As we point to ways forward, we also aim to stimulate reflection and discussion. In a previous book (Angelsen et al. 2012, 2–3), we proposed that REDD+ research is progressing through three generations or phases, mirroring the three phases of REDD+ itself: (i) designing REDD+ and learning from related experiences in the past; (ii) the political economy and implementation of REDD+; and (iii) assessing the impacts of REDD+. The first two edited REDD+ volumes from CIFOR were first-generation research outputs: ‘Moving Ahead with REDD: Issues, options and implications’ (Angelsen 2008) and ‘Realising REDD+: National strategy and policy options’ (Angelsen et al. 2009). The next volume, ‘Analysing REDD+: Challenges and choices’ (Angelsen et al. 2012), moved into second-generation research, analysing actual REDD+ design and early implementation. The current and fourth volume includes research covering all three phases. We have data – albeit far from perfect – that enable us to make preliminary conclusions about the progress and impacts of national and subnational REDD+ initiatives. Yet, the basic design issues (e.g., of results-based payment systems) and coordination and implantation of REDD+ policies across levels and between sectors are still central to the REDD+ debate.