It also bears interesting comparisons to Earth Abides, especially with the beginning of this book set in the Bay Area. But our heroine makes her way into the Rockies, gaining and losing companions from time to time. Some of the best writing and interaction is when she lives on the outskirts of a Mormon settlement that survived slightly better than most of the world due to remoteness and isolation.
Ostensibly a journal, the book occasionally interpolates other stories that the midwife copies into it, but the work as a whole doesn't stick to this formula, to its detriment I think. Certain passages break the illusion, providing information on what's going on in other parts of the world, or giving us the unhappy story of what happens to two former companions after they part ways with the unnamed midwife.
A good read, despite my quibbles.