After the Fall, Before the Fall, During the Fall by Nancy Kress
As the name implies, this apocalyptic story jumps back and forth between times after, before, and during the end time. The book is perhaps more a novella; it is a very quick read though well-written. I enjoyed the way the story was told and the end was intriguing. That said, I didn't really care for the details or plot of the story much because I felt most of it revolved around sex to restart the human population.