Sum: Forty Tales From the Afterlives By David Eagleman Pantheon Books 107 pages; $20 Given the much-repeated aphorism that the only certainties in this world are death and taxation, it's no surprise that many, if not most, of us spend far more time than is necessarily healthy pondering the nature of the afterlife. What awaits us once we've shuffled off this mortal coil? We all have an opinion of sorts; but what always surprises is just how fuzzy around the edges these notions actually are, once we actually get around to fleshing out basic concepts with a bit of detail. Okay, lets accept - for the sake of argument, of course - there is life after death: mental, corporeal, biological, whatever. But what exactly is the afterlife supposed to be like? David Eagleman's Sum: Forty Tales from the Afterlives is a delightful excursion into this gap, offering 40 short vignettes (the longest is four pages) about what could happen to us after we die; a compendium of possibilities. Laced with wry humor and a playful subversiveness, the stories themselves do not demand to be taken too seriously, which is no bad thing in itself. But more than occasionally, something lingers afterward. In "Egalitaire," for example, the reader meets a Supreme Being attempting to rebel against peer pressure to organize the complexities of life along a binary categorization of good and evil. Being an intelligent deity, she - yes, she - doesn't like it, and decides instead to grant everyone a place in Heaven. She has faith in her new system of equality for all, but it doesn't work, of course: "The Communists are baffledâ€¦ they have finally achieved their perfect society, but only by the help of a God in whom they don't want to believe. The Meritocrats are abashed that they're stuck for eternity in an incentiveless system with a bunch of Pinkos. The Conservatives have no penniless to disparage; the Liberals have no downtrodden to promote." So she sits on her bed at night and weeps: "The only thing everyone can agree upon is that they're all in Hell." Elsewhere, Eagleman is less restrained, more direct. In "Mirrors," the afterlife is effectively an aggregation of how other people scattered across our lives have perceived us. It would be a shame to give away the ending of this acerbic little number, but suffice it to say that Sartre would probably agree. If there is a common thread to be found in these short tales, it would be that they are all variations on the theme of uncertainty. Eagleman, a neuroscientist by training, is quite familiar - one imagines - with the all-too-human need to create order and certainty out of randomness and chaos. Certainty, however, demands sacrifices; the paring away of inconvenient facts that divert from our preferred narrative, the excision of the contradictions that make nonsense out of the elaborate - or perhaps not so elaborate - web we construct to give our lives some sense of purpose. Sum is, in essence, about peering into the cracks in the stories that we tell ourselves: what's likely to crawl out when we least expect it? It is worth pointing out that - unlike some of the more strident discursions in the recent past concerning the validity of religion and faith - Eagleman and his book hold no brief for the verity of any particular conception of the afterlife over others. Neither, for that matter, does it allow science to hold sway over faith. If anything, the book is an equal-opportunities jester, poking gentle fun at rigid dogma and orthodoxy, irrespective of how it cloaks itself. Sum, as a work, defies easy description or classification. It refuses to take itself so seriously as to be classified as philosophy, but the profundity of thought popping up unexpectedly elevates it beyond humor. It isn't quite satire, but at the same time, it is as deeply, intimately attached to our comprehension of ourselves and the way we live as to what will happen after we die, that one cannot even begin to consider it fiction. It is short enough to be read in an afternoon, yet dense enough to feed the imagination long afterward. But enough of such attempts to arrange and categorize, trying to place this little gem within a frame of reference. Far better to enjoy it for what it is: an extraordinarily well-written, lucid and enjoyable disquisition into the nature of possibilities.