As the environment deteriorates, so too does American society.
In 2024, Lauren Oya Olamina lives with her father, stepmother, and stepbrothers in a walled neighborhood in the Los Angeles area. Note that this is not a planned "walled community," but a suburban court whose residents walled it in as protection from growing violence and vagrants. This is a serious wall with barbed wire and "lazor wire" on its top, and the keys to the gate are jealously guarded. Her father, a minister of a Baptisty sort of home church, works as a college professor, which he mostly does from home, but has to go in now and then for administrative duties, which is dangerous.
Olamina herself has a serious problem: her mother was using a drug when she was pregnant with her, which resulted in Lauren having a neurological disability that causes her to feel others' pain. It isn't true empathy; she feels it only if she can see it. She cannot believe in her father's religion, and starts keeping notes for her own religion, which she calls Earthseed. It is a bit of a survivalist religion, a bit of a protect-the-earth religion, and its goal, if it has one, is to colonize the stars. Its god is Change. It is actually a very positive faith, with a bit of a Taoist feel to me.
The first half or so of the book is about things Gradually Getting Worse. Lauren's oldest step brother escapes the community, joins a gang, brings the family valuable presents, and is finally brutally murdered. Her father simply disappears on his way home from work. Company towns make a reappearance.There is a new drug going around that makes people want to burn things; fire is experienced as more pleasurable than orgasm.
Finally, in an orgy of destruction, Olamina's community is destroyed by a gang of fire addicts and general looters. With two other survivors, she heads north, looking for a place where she can settle down and start a community of Earthseed. She actually makes converts as she travels, and finds a place. Setting it up as a community is the end of Book One.