I have read the previous book about the people we meet in Heaven, but I do not recollect the exact content, and I have not actually reviewed it. That said, you do not need to know the mechanics of what the concept is, since it happens to the lead character in this book too!
I really enjoyed this book. It is short, and even with the switching in times, it is easily possible to grow to care for all the characters introduced to us.
The fundamental idea here is that no person is just what they appear to one other person. There are consequences and actions that preceded them which have moulded the individuals, and sometimes fate plays its own game.
Annie is a girl who got a second chance at life. She may not have embraced it immediately, but over time, she starts to play a caring and nurturing role in the world. When she dies, she has to take a tour of all that came before and if her final act of selflessness would save a life or not.
There is a gentleness to the writing that feels familiar (I have read a few other books by the author), and it is the kind of book that you finish in one sitting but which lingers long after. I feel like it is one that can trigger conversations in a mixed setting.
I highly recommend the author and this book in particular.