Heather Parry’s Carrion Crow sets out its stall magnificently from the off, throwing the reader right into the deep end of a claustrophobic gothic grotesque. It catalogues one young woman’s steady descent into incarcerated madness, becoming, as it goes, exponentially unsettling and increasingly stomach-churning.

Marguerite Périgord lives a stone’s throw from the “shit-stink” of the River Thames in Victorian London with her family in a crumbling house that once was grand, but is no more. She has been confined to the attic, the sinister opening lines convey, “for the sake of her wellbeing. That’s what her mother had said.”

Marguerite is the oldest daughter of Cécile Périgord, a woman who comes from new money – her father made soap for the queen - but who has since lost her tenuous grip on London high society after the departure of her husband, a man whose flagrant sex obsession has mired them in scandal. Marguerite is to be married to a much older – and significantly poorer – solicitor, but Cécile, whose general view of men now is understandably dim, does not approve. She locks her daughter away so that Marguerite can properly prepare herself for wifedom, and leaves her with the collected works of Victor Hugo, Mrs Beeton’s Book of Household Management and a sewing machine. Each evening, more or less, Cécile visits with a plate of sustaining food.

But Marguerite worries that she might have been forgotten. Time slides. “She understood that by now she must be older than when first she entered the attic; that there would be much less of her, no swell at her hips or breast, nothing to fill her cheeks up when she smiled.”

A writer from Rotherham now living in Glasgow, Heather Parry is the author of one previous novel, a short story collection and a nonfiction work on capitalism, each of which found more plaudits than they did readers. This should change with Carrion Crow, which, surely, will win awards. Victorian London is reliably fertile ground for novelists. There is so much refinery, so much contrasting squalor; Parry prefers, and revels in, the latter. Her depiction of it, so vivid, makes the pages squelch.

Locked away, Marguerite grows increasingly lonely. She can hear her siblings down below but can no longer access them, and her mother’s nightly visits seem far less regular. Craving distraction, she indulges in self-exploration, no cavity too inaccessible. “Marguerite found that the insides of her ears were thick with a mustard-coloured wax.” Beneath one fingernail she finds a woodlouse, “so old as to be fossilised”. On particularly drab days, “she could entertain herself for hours with the investigation of her own tonsils”.

Hunger conjures its increasingly hypnotic spell, and she develops by necessity an adventurous palate. When a crow nesting alongside her brings worms back, Marguerite swipes one and pops it into her mouth. “There she let it move, drawing moisture from her dry gums. She bit it into two wet halves, chewing it into a cud. It was orange jelly, it was veal cake, it was fricasseed turkey. A banquet for one.”

Gradually, we come to learn more of Cécile’s own nervous disposition, which may explain her maternal cruelty. Cécile is greatly reduced herself, cut off from her parents, adrift. But her steel remains. Reputation is at stake. When her daughter says, “Mother, I am rotting here”, Cécile barely flinches.

The more Marguerite diminishes in her confinement, the more Parry comes into her element. Every sentence oozes a crushed purple poetry, overripe with devastation and wretchedness. Marguerite’s plight is clearly one of tragedy, but it is thrillingly told, and you cannot look away. The film adaptation will carry an 18 certificate.

If you finish it feeling you might just skip dinner, then you also feel filled with awe for a writer so gifted at conveying this much ick in such luxuriant, refulgent style.

• Carrion Crow by Heather Parry is published by Transworld (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply