(Pantheon, 128 pages, $25)

However popular heaven may be as an idea, says author David Eagleman, few of us spend much time imagining possible afterlives in any detail. People like to say that in death you’ll be surrounded by the people you loved. Does that mean your new world will look like this one, except emptied of the people you didn’t like? And what about all the people you thought were just okay? Maybe God won’t be a white-bearded gent but an entity so vast that her attempts to communicate with us will remain as futile as reading Shakespeare to a virus. Or maybe it’s God who is “the size of a bacterium”—indifferent to beings our size but obsessively concerned with the fate of the microbes that will spill from our dead bodies.

Eagleman has sketched out 40 such scenarios in his “disarming, splendid little book,” said Joy Tipping in The Dallas Morning News. The fact that he’s a neuroscientist might lead you to expect that many of his thought experiments will have “an atheistic leaning.” Instead, a maker or creator figures in most of them, and virtually all provide an intriguing reflection on life as we know it. In one of Eagleman’s possible afterlives, said Fritz Lanham in The Houston Chronicle, “you run into all the yous that you might have been had you made different choices.” In another, the myriad events of your earthly life are collated in such a way that teeth-brushing becomes a 35-day marathon and you tell lies for 48 hours straight. Sum is a marvel. “I can’t think of another book quite like it.”

Eagleman’s ultimate message is a bit of a letdown, said Andrew Stark in The Wall Street Journal. Though the book could hardly be more “imaginative and inventive in its approach,” all it seems to tell us about life is that we ought to attend more to the wonders of the present moment. “Hardly a new idea,” in other words. Still, Eagleman is able again and again to “convey sharp insights about how we think about death.” He notes at one point how lucky we are that our minds tend to envision future events as if they were indistinct dots on a distant horizon. For most of our lives, the Grim Reaper himself appears to be no threat at all.