I'd forgotten the review that made me reserve David Eagleman's "Sum: Forty tales from the afterlives" at the library, so it came as the surprise it needs, for full effect, to be.
Forty pieces (essays? meditations? fables? science fiction flights of fancy?) each propose some different idea of an afterlife, and let it run.
Suppose there are all the "yous" that ever were, or might have been: what would that be like? Suppose there are only the people closest to you in life, and nothing of what was in the background: "The missing crowds make you lonely. You begin to complain about all the people you could be meeting. But no one listens or sympathizes with you, because this is exactly what you chose when you were alive."
Or consider it from the point of view of the atoms of which we are composed, disbanded like a platoon of soldiers or the cast of a long-running play: "They part ways, moving off in their separate directions, mourning the loss of a special time they shared together, haunted by the feeling that they were once playing parts in something larger than themselves, something that had its own life, something they can hardly put a finger on." But, in another piece, "In the form of a human, the atoms suffer a claustrophobia of size... And in this form, they find themselves longing to ascend mountains, wander the seas and conquer the air, seeking to recapture the limitlessness they once knew."
Each piece is a miniature, almost a prose poem, no more than a couple of pages long, but a delayed-action idea-bomb, waiting to knock off-kilter your perspective on this life.