It's set in a post-collapse world, but as it goes along it shows us that there can be different degrees of post-apocalypse when it comes to individuals. The first third shows the main character in the context of her family trying to do everything they can to safeguard their home, and the remainder shows what happens as it ends up failing for them. What saves Lauren is her ability to think for herself and look beyond what was immediately in front of her, though it is abundantly clear that a lot of it is a matter of luck too. By the end, she has assembled a sort of replacement community from people who were once strangers, who all have come to accept her ideas on the reasons for human existence. It becomes a sort of picaresque novel by then as the group encounters different challenges walking the California freeways to a hazily defined destination up north.
Lauren is a Sharer too, experiencing the emotions and feelings of those she sees whether for good or ill. It is almost as if this is a separate aspect of the story, it influences the character's behavior in situations but doesn't really play a fundamental role in driving the plot I think. Maybe if the author were able to write the later volumes in the series this condition would have been more deeply integrated as an element.
This edition of the book includes the first three chapters or so of Parable of the Talents. I expect to finish that book also later this year to find out how this near-future depiction of the US plays out. There has been a lot of talk recently about how prescient Butler was in discussing topics which are currently hot in the real world and I do want to know how far this extends.