In recent years the reimagining of Greek myth has become almost a genre in itself: from classicists such as Madeline Miller and Natalie Haynes to Margaret Atwood and Colm Tóibín, modern writers have found fresh ways to spin these ancient stories. Many seek to foreground the experiences of women overlooked in the originals; only a few come close to matching the sharp perspicacity and profound humanity of Pat Barker.

The Voyage Home, the third volume in her masterful reimagining of Homer’s Iliad, takes up the tale exactly where The Women of Troy left off. After 10 grisly years of fighting, Agamemnon and his men are sailing for home. Their ships are laden with the spoils of war, including many hundreds of Trojan women, who have been shared out among the conquerors and taken as slaves. One of those slaves is the priestess Cassandra, daughter of King Priam, whom Agamemnon has not only claimed as his prize but secretly married. In Mycenae, meanwhile, his wife, Clytemnestra, is preparing for his return. A decade has passed since Agamemnon sacrificed their daughter Iphigenia to the gods for a fair wind to Troy, but Clytemnestra’s grief and fury have not dimmed. As Cassandra bleakly foretells, a violent reckoning awaits.

In The Silence of the Girls and The Women of Troy Barker set aside the bloody glories of the battlefield to focus instead on the women captured and taken as slaves. Vivid and visceral, ringing with grief and anger and the powerful will to survive, the books gave silenced women full-throated voice to expose the brutal and profoundly unheroic realities of war.

Something rather different is going on in The Voyage Home. Told over four days, the novel moves away from the extensive sorority of the slave camps to cleave closely to the story’s main protagonists, Clytemnestra and Cassandra. As the prophet cursed by the spurned Apollo that her prophecies should never be believed, Cassandra is perhaps the most notoriously silenced woman in literary history: her prophecies, she notes drily, have “only been believed when I could get a man to deliver them”. The murderous Clytemnestra, merciless matriarch and archetypal all-round Bad Wife, is a different kettle of fish. In Agamemnon’s absence she is said not only to have seized his throne but to have taken his estranged cousin, Aegisthus, into her bed. Clever, fearless, duplicitous, insatiably hungry for power and driven by a furious desire for vengeance, she has all the reckless swagger of a (male) Greek hero.

In The Voyage Home Barker strips away the glittering armour of myth to expose the queen’s private self. Her Clytemnestra is no termagant. She is a shrewd and capable ruler, but she is not driven by power. Though Aegisthus tries – and everyone gossips – she has no interest in sex. Her husband has broken her heart and, after 10 years of grief and anger, she is quietly, fiercely, resolved to settle the score. She is also still a mother: while manoeuvring to protect the throne for her absent son Orestes, she struggles to parent Electra, an anorexic, eczema-plagued teenager plainly ravaged by trauma.

By contrast there is something disconcerting, even dislikable, about Barker’s yellow-eyed Cassandra. With her penetrating grasp of people’s private thoughts and her complete indifference to their feelings, she is closer in temperament to the gods than to her human companions. Her unknowability is emphasised by Barker, who leaves it to Ritsa, Cassandra’s no-nonsense body slave, to narrate most of her side of the story. Ritsa describes her mistress as “mad as a box of snakes”: she vacillates between grudging tenderness for Cassandra and a reflexive antipathy. She refuses to regard her as a victim but then, as she caustically observes, “I knew her better than most.”

The squalor of the rape camp may have given way to the marble splendour of Mycenae, but in Barker’s telling the shadows of horror still stretch long. Decades earlier, in a stunningly grotesque grab for power, Agamemnon’s own father had invited his brother Thyestes to dinner, revealing only when the meal was finished that the meat Thyestes had praised was in fact the flesh of his own infant sons. Now those horrifically butchered boys haunt the palace like a spectral Greek chorus, their cackling voices seeping from the walls. “Singing like songs could kill”, they chant nursery rhymes with malicious relish: “Here comes a candle to light you to bed, here comes a chopper to chop off your head!”

Ever since Aeschylus set Clytemnestra centre stage in the first play of the Oresteia, this bloody tale has reverberated down the ages. With her characteristic blend of brusque wisdom and piercing compassion, Barker remakes it for our times. “You don’t always need hope,” Ritsa observes as the Trojan slave women raise their voices in lament. “Sometimes it helps just to have your despair recognised, and shared.” Clytemnestra and Cassandra are two women with every reason to despair. This strikingly accomplished novel compels us to bear witness to them both.