Christiana Figueres and Tom Rivett-Carnac--who led negotiations for the United Nations during the historic Paris Agreement of 2015--have written a cautionary but optimistic book about the world's changing climate and the fate of humanity. How all of us address the climate crisis in the next thirty years will determine not only the world we will live in but also the world we will bequeath to our children and theirs. The authors outline two possible scenarios for our planet. In one, they describe what life on Earth will be like by 2050 if we fail to meet the Paris climate targets. In the other, they lay out