The Overstory by Richard Powers is an exploration of American society's relationship with nature. He builds upon the work of pioneers in the field, like Thoreau, and offers a fresh perspective that's meant for our modern times. The story is told through a series of vignettes that each focus on a different character's relationship with trees. Powers also explores the idea of trees possibly having agency and how they interact with one another to build communities.
Because of the way the story is told, Powers is able to explore a variety of themes. For example, one chapter focuses on a Chinese immigrant and his family. In this story, Powers is able to weave an exploration of immigration, Asian identity, and family politics into his look at this family's relationship with nature. There's another section where Powers explores the story of a man who participated in a prison study. He and a group of volunteers were put in prison so that psychologists could study their behavior. This chapter allows Powers to talk about issues relating to prison and being confined to a cell while also talking about nature's power to help heal some of these wounds.
There are dozens of examples like this throughout the novel. The focus of The Overstory is definitely on mankind's relationship with nature. However, that doesn't mean Powers limits his discussion to those topics. Rather, he also spends time exploring concepts like the ones listed above. This makes for a multi-faceted look at the human condition that Powers masterfully places alongside our relationship with the natural world.