America is an increasingly strange place these days, but perhaps the strangeness was always lurking in the things that made its culture seem familiar, even comforting, to those who were reared elsewhere. Take, for example, the use of the word “God”, who is always blessing America. He is not much invoked by politicians on this side of the Atlantic (except in Ulster, where He also did a great job), because we would find that specious. Nor do we have religious novelists, like the great Marilynne Robinson, who writes from a place of belief and teaches theology in her spare time. Faith and the problems of faith still animate American fiction. Even the bloody sacramentalism of Cormac McCarthy can feel religious, if only by opposition. Like Robinson, Joy Williams is acquainted with the devil and she knows what it is to be saved. Williams’s father was a congregationalist preacher and her grandfather a Welsh Baptist minister. She has the same spiritual rhythms as Robinson, but the stakes are higher in Williams, and a lot more fun. She does horror and incomprehensibility as well as the ecstatic, and she does it all deadpan. I want to say that if you banged a Robinson novel off one by Cormac McCarthy, the sparks that flew would be something like Williams, except that neither of those writers does funny and Williams is the kind of funny you can’t explain. In her new collection Concerning the Future of Souls: 99 Stories of Azrael, the humour comes from Williams’s wryness and her brevity, the way she whisks a joke away, obliging the reader to follow on. Williams does horror as well as the ecstatic, and she does it all deadpan Concerning the Future of Souls is not a novel and it is not exactly a book of linked short stories: it has many ideas and no plot, yet it is hard to put down. A kind of philosophical bait and switch keeps the pages turning. The laugh is often in the title which comes at the end, like an art gallery label or the caption on a cartoon, and these titles sometimes negate what has come before. Azrael, the angel who transports souls after death, has 4,000 wings and a melancholy air. He doesn’t travel in the same circles as Jesus, and his discussions with God are pretty brief. He chats instead with the Devil, who has eyes of indigo blue and never wears the same shoes twice. Azrael is worried about the deaths of trees, because “the forest had been a living being and now it was not”. Also, the great depletion of species means that transmigrating souls have nowhere left to go. He thinks humankind is coming to an end of sorts. “They were about to tear the place down any minute and they had actually.” Meanwhile God, being God, is taking a larger view: “The existence of creatures and their nonexistence are the same.” This is a book of erasures. Interleaved with Azrael’s conversations are short accounts of various deaths, some of them absurd, along with thoughts about time and particularity. The book is interested in the mortality of animals as well as of human beings and trees. There are whales, elephants, dolphins, a beautifully tended cow, a single ant. Most of the people doing the dying are men, for some reason: they include Dylan Thomas, Nabokov and Thomas Merton, an American monk of great purity who was killed by an electrical fan. The voice is one of unloosed, unstoppable intelligence. There is a really good joke about Rilke and a great one-liner on the death of Mrs Muffin, Robert Lowell’s guinea pig. It is possible the reader will find these funny even if they don’t read poetry, but, as Williams herself might point out, you cannot read this book without knowing what you already know. On the way through, I Googled many interesting things: images by Tischbein and Gustave Doré, the theological difference between knowledge and understanding, the meaning of the words “wyrd” and “tetrachromatic”, Bergson’s cone of memory. This is the first text I have read in which the cone is a unifying theme, from the dunce cap of Duns Scotus to the sandglass of time. A certain kind of reader will find all this exhilarating, though they might be a tiny bit embarrassed to admit as much. Those who are new to Williams’s work will reach immediately after reading this for The Visiting Privilege, a selection of stories spanning 40 years, where they will find a more naturalistic kind of gothic tale. Concerning the Future of Souls forms a companion to 99 Stories of God, published in 2016. It also stands alone, however, and the statement it makes about time and narrative is very moving. “More and more Azrael was arriving too late for the world.” The book reads like a slowly unravelling jumper, undoing itself stitch by stitch. “You dream a dream according to one order and remember it in another, Azrael said calmly. To make it more comprehensible.” Williams is now 80. This is a book completed, after many other good books, by a master of the craft. Prepare to be moved. Concerning the Future of Souls: 99 Stories of Azrael by Joy Williams is published by Tuskar Rock (£12.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.