Patti Callahan, the author of “Becoming Mrs. Lewis” is, in fact, Patti Callahan Henry, bestselling and prize-winning Alabama author of 13 volumes of fiction, most recently “The Bookshop at Water’s End,” one of a series of books in which a female protagonist has her life disrupted, by illness, accident or most commonly, a rotten husband, and has to regroup. She does this with the aid of supportive friends and there is usually a happy ending.

Usually the setting for these popular novels is the contemporary American South, often in a seaside town.

“Becoming Mrs. Lewis” is a very different kind of novel and Henry deserves credit for risking disappointing her large readership. The name change is not meant to disavow her other work but to distinguish this novel from her usual settings and subjects.

This is the fictionalized autobiography of Joy Davidman, an accomplished American novelist, magazine writer, biographer and poet.

In 1946, Joy is living in upstate New York, in the Hudson Valley, with two little boys and her husband Bill, who fought in the Spanish Civil War and now suffers from PTSD.

Bill is depressed, alcoholic, sometimes suicidal, flagrantly unfaithful, potentially violent.

Under unbearable pressures, Joy, a Jewish atheist, falls to her knees, prays for help, has a moment of grace and becomes a devout Christian.

Davidman describes it this way: “In the crack of my soul, during the untethered fear while calling for help, … God came in: he entered the fissures of my heart as if he’s been waiting a long time to find an opening. Warmth fell over me, a river of peace passed through me. For the first time in my life I felt fully known and loved.”

Some three years later, after having read and reread the books of C. S. Lewis, himself a convert from atheism, Joy decides to write Lewis, hoping for a little guidance. We might know Lewis primarily as the author of the “Chronicles of Narnia” and good friend of J.R.R. Tolkien, but he was also a most influential commentator, explainer, of Christianity in such works as “Mere Christianity” and “The Screwtape Letters.”

Lewis, who would ultimately be the author of 30 books, a genius, bachelor eccentric in his 50s, and a don at Magdalen College, Oxford, replies, and a correspondence is established, at first quite formal, intellectual, mentor to student, and then more as friends and equals.

Joy visits England and they become close.

The two meet, talk, walk along the river and among the spires of Oxford, read and help with each other’s works in progress. The relationship is warm, companionate. They are, clearly, soulmates. Joy falls in love, maybe Lewis does, too, but his very strict theology keeps him chaste. He explains they may enjoy several kinds of love, but eros is forbidden.

This is perplexing and a little distressing to Joy, who has a strong libido and had “pursued men with embarrassing voracity” in an unsuccessful attempt to find solace, to fix her loneliness.

Even when she moves with her two boys into his lovely estate, “The Kiln,” outside Oxford, they maintain their chastity.

“Somehow I felt that we were a new kind of family. Who was to say there was only one way to love someone? I knew he loved us: words didn’t have to be spoken. And this, for now, would be enough.”

His faith and very literal and rigid understanding of the commandments prevents intimacy for what seems to Joy — and the reader — forever.

Even after Joy’s divorce, Lewis is uncertain — after all, marriage vows are “till death do us part.”

Finally, after exasperating Joy and us, Lewis relents. The couple hold hands, even kiss and as the title suggests, in 1956, finally, for only a few short years before her death from cancer, Joy becomes Mrs. Lewis. No spoiler there.

“Becoming Mrs. Lewis” is a quiet, sensitive and singular story of an intellectual and deeply human relationship that grows slowly over time. It’s an unusual love affair, to be sure. There are, obviously no sex scenes, no violence, drugs, rock and roll, car chases, shoot-outs or explosions, but the story still moves.

Callahan Henry uses biographies of Lewis and Davidman for the facts, then creates scenes, dialogue, even interior monologues to bring the story and the characters to life. It is a satisfying read and finally, as odd as these people are, we cheer them on.

Don Noble is host of the Alabama Public Television literary interview show “Bookmark with Don Noble.” His most recent book is Belles’ Letters 2, a collection of short fiction by Alabama women.