The main theme of the book is how to win the fight against climate change. The authors focus on what humanity needs to do (as of 2020) to successfully combat the effects of climate change, while warning that success is not assured. In Chapters 2 and 3, they present two scenarios of what the world could look like in 2050: one in which humankind does nothing and one in which it works together and fights climate change. This is intended to grab the reader’s attention and galvanize their commitment to the fight.

The rest of the book presents strategies for winning the fight. However, the authors do not jump straight into “practical” steps. Instead, they spend three chapters (the fifth through seventh) discussing the shifts in mindset that taking on the challenge necessitates. They argue that for true transformation—not merely incremental improvements—to take place, “we have to change how we think and fundamentally who we perceive ourselves to be” (38). These mindsets include stubborn optimism, endless abundance, and radical regeneration. The significance of these mindsets to climate activism varies. Stubborn optimism largely provides the movement with the strength to keep going, but endless abundance and radical regeneration both have direct implications for humanity’s relationship to nature; to win the fight against climate change, the authors argue, people cannot continue to view the environment as something separate from humankind.