This book has one of the most interesting concepts in a book I've come across in a long time. That there is something between life and death, an in-between state where you can re-do your life, to an extent. You get a series of what-ifs to live through to see if they fit better. An infinite number of second chances.
The book transitions slightly into a question of quantum mechanics and a discussion with another slider (the term given to people who can hop from life to life in that in-between period) around the many-worlds theory doesn't really go anywhere.
I would have liked to seen this area explored more, the experience and the universe of the characters that exist here. For example, who are the people that exist on the cusp of life and death, why are they there, does everyone who dies spend time there, or are only some chosen, and why? This would have been a great way to learn more about the peripheral players.
But this element of the plot seemed to be shoehorned in to give some sort of scientific basis for the way the book was shaped. Like many of the characters, not fully developed, and more set dressing than real life people with their own agency. Even Nora, the main character was poorly drawn. Maybe because we spent so much time with her when she wasn't actually her, all we learned about her for most of the book was what she didn't want to be, not who she actually was.
It felt like the author was trying to write a small story about big ideas, about depression and how it informs us, but fell short of making something truly important, and never quite manages to pull it off.
The ending was as predicable as I'd feared, but strangely enough was the best part of the book. It was delicately written with real warmth and a feeling of hope just pored through the final pages. Just about redeemed the whole book.