From this fascinating book, I come away with the thought that our lives hang by threads and could easily have been different. Of course in real life time is linear and unalterable, but in our minds we imagine differently.
John Whittier wrote, "For all sad words of tongue and pen, The saddest are these, 'It might have been'."
The book is confusing, jumping around in time and place. These websites are helpful: https://www.shmoop.com/life-after-life/ and https://www.litcharts.com/lit/life-after-life
Each has a plot summary and list of characters. Also, I like the author's comments. http://www.kateatkinson.co.uk/book_detail.php?b=Life_After_Life
One reader complained about the quotes from foreign languages. Yes, the author was snobbish to omit translations. These can be found on the Internet, either searching the quote or using Google translate (not reliable). For instance, in the chapter "Like a Fox in a Hole", the author describes a demonstration by desperate veterans and quotes Dante describing people going to hell:
"Si lunga tratta di gente, ch’i’ non averei creduto che morte tanta n’avesse disfatta."
I translate this: "Such a long procession of people; I never would have believed that death had undone so many." The implication is life can be like hell.
If you liked this book, read the sequel, A Life in Ruins.