Marilynne Robinson’s new book is one of the best American novels published this year. Some readers may be put off by the novel’s thoroughgoing Christianity. But no better case has been made in recent years for the rich artistic possibilities special to a Christian worldview.

Ms. Robinson’s only preceding novel, published a quarter-century ago, is the now-beloved “Housekeeping.” A damp book, set among the shifting groundwater of the upper Rockies, it was about the disintegration of an all-female family. Its characters seemed almost mute, and their eccentric ways – eating dinner in the dark, giving up on housekeeping – were ably but incongruently animated by Ms. Robinson’s warm and conscientious voice.

In “Gilead” (Farrar, Straus & Giroux, 247 pages, $23) that voice finds a home in a terminally ill preacher, John Ames, who is composing his memoirs as a testament for his 7-year-old son to later read. Ames writes like a preacher. He is on guard against totalizing statements, about which he must say, “That’s the pulpit speaking.” He is capable of sentences like: “Now that I look back, it seems to me that in all that deep darkness a miracle was preparing.”

A belief in miracles is great ballast for the interpretive mind. It is the preacher’s habit to see agency – God – in everything. This can seem softheaded, especially in smarmy constructions like “a miracle was preparing.” But for a novelist, who by trade is already dedicated to wringing meaning out of disconnected events, this is good religion.

In an essay about her first childhood intimations of God, Ms. Robinson has written that at first she “was aware to the point of alarm of a vast energy of intention, all around me, barely restrained, and I thought everyone must be aware of it.” In her adult work, she bathes her reader in the same energy. Ames, as spiritual interpreter for a community, takes some of the burden of divine attentiveness upon himself.

“Any human face is a claim on you,” he writes, “because you can’t help but understand the singularity of it, the courage and loneliness of it.” In surmising the needs of others, he is like Henry James, on whom nothing is lost. Ames sees old Bible stories a fresh, finding comfort in the story of Hagar and Ishmael’s banishment. He reasons, humbly but boldly, that his surviving wife and son will be like those two.

Because Ames has always viewed every detail of the world as a gift from God, he is even able to remember how, when entering the church on mornings decades ago, he always “loved the sound of the latch lifting.” In places like this it is hard to distinguish Ms. Robinson’s experience with faith from her gifts as a novelist.

Ms. Robinson may challenge readers who are ready to condescend to a preacher’s voice, and she seems to know this. Certainly Ames does. Writing in an unspecified postwar period, he senses the coming amnesia about theological richness. In answer to our, or his son’s, probable questions about Ames’s unworldly style, he writes, “There is an earned innocence, I believe, which is as much to be honored as the innocence of children.” He means that it takes effort to strip away the “accretions of smugness and pretense and triviality” that would put a cosmopolitan bounce in his voice.

A defensive posture, sometimes even an embarrassed one, is increasingly expected – and common – in literature coming out of Middle America. But Ms. Robinson grounds her subjectivity in Iowa, not in Iowa-via-New York. Ames envisions: “An old fire will make a dark husk for itself and settle in on its core, as in the case of this planet.” Ms. Robinson conjures the prairie’s flat horizons and its fire without surrendering the global ambition of any local literature.

The plot of “Gilead” is robust and tragic. As Ames withers, his wastrel godson returns to town and befriends his wife and son, to the preacher’s chagrin. This Jack is permanently skeptical but can’t keep himself from the preacher’s counsel. Ames does not know how to explain Jack’s lack of faith to Jack, and he doesn’t know whether he should warn his wife about Jack – or forgive Jack, as the ministry would demand.

In the end, “Gilead” demonstrates the differences between the mind of Greek tragedy and the mind of Christianity. Ames closes his long letter with mention of “prevenient grace,” that grace which, in theology, first comes from God to the sinner so that the sinner has the courage to then repent and ask for the full measure of grace.

Ms. Robinson makes a similarly prevenient appeal, offering her honesty as a promise of fuller enjoyments for readers who, after hesitation, give themselves over to her excellent book.