For anyone doing #pop22 ... I read this book years ago and loved it. It would fit very well with the prompt: a book about the afterlife... written as a series of thought experiments, it provoked all sorts of feelings.
If I was deeply religious or held strong ideas about what the afterlife would be like, it wouldn't be for me, but as someone who likes to play with big ideas and tickle a feeling of existential dread - it's a masterpiece!