In 2012, after a wildly successful and hectic period during which he worked almost exclusively as a playwright, the Norwegian author and dramatist Jon Fosse converted to Catholicism, quit drinking, and remarried. He then started composing “Septology,” a seven-volume novel written in a single sentence and exemplifying what he has described as his turn to “slow prose.” (The book was translated, by Damion Searls, for Fitzcarraldo Editions, in the U.K.; a U.S. edition is out this month, from Transit Books.) The novel’s narrator is a painter named Asle, a convert to Catholicism who’s grieving the death of his wife. The night before Christmas Eve, he finds his friend, also a painter named Asle, unconscious in an alley in Bergen, dying of alcohol poisoning. Their memories double, repeat, and gradually blur into a single voice, a diffuse consciousness capable of existing in many times and places at once. Though lacking a particularly doctrinal or dogmatic sense of religion, the novel raises the possibility of belief in the reality of the divine, as the fourteenth-century theologian Meister Eckhart, whom Fosse has read intently, describes it: “It is in darkness that one finds the light, so when we are in sorrow, then this light is nearest of all to us.”