After millennia joined at the hip, art and faith largely parted ways, at least in terms of art as the aesthetic expression of religion. What dialogue the two have had over the past century or so has been – from art’s side, anyway – a bit antagonistic and largely ironic. Intellectual life generally has become secularised.

How, then, are we to read a novel in which the protagonists – intellectuals, academics, adulterers – are believers, their struggles conveyed not with irony but with earnestness? How, from the writer’s point of view, to convey the weight of sin, the claustrophobia that must result from its commission, when writing about characters who have faith?

Jamie Quatro’s 2013 book of short stories, I Want to Show You More, dealt with many of these concerns. Again and again, we saw women – Christian, married with children – coping with their own adulterous desires. The collection was rightly lauded; it contains several excellent stories. But a story is unlike a novel in important ways other than length. Its glancing and elliptical nature means a writer can allude to things without having to go into great detail – and if the alluding is done well, whole worlds can be conjured within a few pages, without ever having to risk the narrative collapsing under the weight of the improbable or ideas going limp under the strain of too prolonged a focus. In a novel, though, there’s no hiding. 

Quatro’s debut novel, Fire Sermon, tells the story of Maggie, living in Tennessee, raised evangelical, married young. Thomas, her husband, is almost ludicrously dutiful: he remembers that Maggie likes her coffee mug pre-heated for 23 seconds and that he must alternate sides when putting the baby to sleep, to ensure the development of an evenly shaped head. 

But there is a restlessness in Maggie, and over the years, as their children grow and the marital bed turns cold, she is tempted. When she meets James, she finally acts. James is a poet, a Christian, and a Princeton academic; he’s part of the Occupy movement (but thoroughly bourgeois), and his poetry is “recalibrating the language of faith”. To Maggie, who has spent her life with an agnostic financier, he’s irresistible. 

There is a disconnect between, on the one hand, the age in which Maggie and James are living and their milieu and, on the other, their heartfelt theological banter – and this is part of the point: these are people out of time.

At one point, in an exchange with an unnamed interlocutor – presumably the inner voice of conscience and reason – Maggie ponders whether she might actually be lying to herself about her beliefs in order to fuel the pleasure of transgression; she admits that unless something is forbidden, she “can’t fucking feel anything”. These are juicy ideas, and a darker, less earnest novel might have successfully explored them. But Quatro fails to weave the ideas driving the narrative into the actual events, and we veer between a didacticism, in which Maggie intellectualises her desires, and the affair itself, often rendered in language that is cloyingly intimate, insufficiently sieved. The gap leaves the God issue feeling tacked-on and not entirely convincing.

There are moments here that have the strength of her stories. A brief church scene from Maggie’s childhood, where people “cried, or made typewriter sounds with their teeth, their hands stretched out like they wanted something”. The discovery that her daughter is pulling out her own hair: “From the back of her head sprouts what looks like the tip of a tiny saguaro cactus.” A confession from a young boy – sexual in nature, naturally – the year Maggie and her husband work as houseparents at a boarding school. 

But too often, the writing doesn’t hold up. There are diary entries in the form of letters to James that read – alas – like a teenage girl’s diary entries. There is Maggie picturing Jesus on the cross embracing Manhattan: “The horizontal beam became a pair of arms and wrapped the island up, as if the cross were hugging a pillow to its chest.” The head talks to the heart: “Deluded Heart, you’ll only make a mess.”

To return to the question we began with, of whether and how a contemporary novelist might get beyond, as David Foster Wallace put it, the stance of “self-consciousness and hip fatigue”. As Elaine Blair has written, Wallace found his answer, in Infinite Jest, in the culture of recovery, where survival depends on sincerity. But there is a black humour that runs through 12-step culture that saves it from being simply sincere. It’s not that there’s no irony in recovery; it’s that irony knows its place. 

Quatro’s realm is trickier to write. At one point, her protagonist longs for the return of a “viable literature of faith”. It isn’t clear we’re capable of that.

• Molly McCloskey’s novel, When Light Is Like Water, is published by Penguin. Fire Sermon is published by Picador. To order a copy for £12.74 (RRP £14.99) go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99..