Donal Ryan’s third novel is a departure for him. With his previous two books he cruised along easy street with tales of woe and tragedy that picked up praise and rewards on the way, their unlikely heroes plucking at our heart strings. Here, with his female antihero Melody Shee, Ryan turns his back on the formula and veers off-road. Expect a bumpy ride.

Melody is 33 and has just informed her husband – who “13 and a bit weeks ago was the only boy I’d ever kissed” – that her unborn child is not his. A 17-year-old Traveller named Martin Toppy, whom she taught for more than a year, is the father.

Our protagonist is a horrible person who has been in a toxic, destructive relationship for too long. On discovering her husband has been using prostitutes, she secretly delights in the news so she can “fashion a scalpel from [it] to silently flay him”. It’s refreshing to find a repulsive protagonist in a novel by one of Ireland’s most successful contemporary writers.

Melody is an educated woman who has written poetry for the local newspaper (this would explain her poetic descriptions and keen observations of the weather and people). She has also written articles on assistance for asylum seekers and abortion.

However, this is all exposition. In the narrating of her life, we get no sense she has an opinion on abortion other than one fleeting mention of London (a euphemism for abortion in Ireland) while she considers what to do with her pregnancy. Nor do we get a sense of her feelings about class issues or discrimination against Travellers other than correcting her father and husband for using derogatory terms. The reader is left on the surface of her psychological landscape, unable to delve into what should be a really interesting character.

Refreshingly, Melody refuses to be a victim like the many narrators of Ryan’s other novels. But as if to offset this denial of easy sympathy, every other character becomes weak and needy. Within the opening 40-odd pages, everyone (other than Melody) cries: Melody’s husband on hearing about the pregnancy, Martin Toppy when he first arrives to be tutored, Melody’s father at the kitchen table, her childhood friend, Breedie, and a young Traveller woman, Mary. It is unrelenting.

To his credit, Ryan does attempt to give voice to the Traveller community. The two teenage Travellers in the novel are illiterate, though 19-year-old Mary has the “taste of a vision” and is something of a mystic. Martin’s father is a famous bare-knuckle boxer and Martin himself will follow suit. Here, the novel follows a well-worn path of violence between Travellers, with shootings, knee-cappings, slashings, family feuds (even a mother carries a shotgun) and scores being settled “one on one”. For a writer of Ryan’s obvious talents, it seems like a missed opportunity for an underrepresented community to be portrayed in such a negative, cliched way.

It is the flashbacks to Melody’s relationship with Martin that gives the book much of its colour, but the moral consequences of her actions – seducing a boy of 16 over the course of a year – could have been examined in more depth.

Undoubtedly a departure for Ryan, All We Shall Know is a brave attempt at extending his oeuvre. It might just be an extension too far.

Kevin Curran’s second novel, Citizens, is out now. All We Shall Know is published by Doubleday (£12.99). Click here to buy it for £10.65