In Yann Martel’s fifth novel, a Canadian classicist, Harlow Donne, has been offered a year’s fellowship at Oxford University. His wife, Gail, has a full-time managerial job, and they have a seven-year-old daughter, Helen. Who will pour out her breakfast cereal and pick her up from school while Harlow is away? He and Gail quarrel. He leaves for England, and as she sees him off Gail whispers in his ear: “Don’t come back.”

So far, so everyday: but once Harlow gets to Oxford, the narrative shifts its form and becomes odder and more interesting. His prescribed task is to help sift through and translate a hoard of ancient papyri from Oxyrhynchus, in upper Egypt. It’s tedious work. Soon, though, Harlow is piecing together from words or half-words on wisps of desiccated reeds what he believes to be a long-lost epic poem. It relates the story of the Trojan war, but not, as Homer tells it, from the viewpoint of princely warriors and gods. The protagonist is a common soldier, a “son of nobody” named Psoas.

This is not just a novel about a poem: it actually contains that poem. The Psoad makes up half of Martel’s book in terms of word count, and most of it in terms of creative energy. The poem’s fragments are printed across the top half of the pages, while below the line are footnotes, in which Harlow sets out to comment on the text, but is soon finding in it prompts for reminiscences about his relationship with Gail, and reflections about his home life addressed to his daughter. The two narrative strands – the ancient epic and the modern domestic drama – tug at and distort each other, until finally they merge in a doubly mournful conclusion.

It’s not a brand new form – think of Nabokov’s Pale Fire – but Martel handles it ingeniously. As in Pale Fire, we readers become suspicious of the scholar’s motivation: is Harlow actually fabricating this supposedly ancient text as a vehicle for his own resentments, his own love, guilt and grief? Certainly his supervisor thinks so; he compares the Psoad to Frankenstein’s monster, “a corpse with a thousand stitches”. But Harlow (or rather his creator) has the skill to carry readers along.

The Psoad, 30 fragments of which are presented here, is a compelling narrative poem. Written largely in iambic pentameter, it is varied and enlivened by salty dialogue and songs. It has vivid detail, jokes and puns, plot twists and sardonic commentary. Martel shifts the focus of the story away from the heroes; his Greeks include merchants, more knowledgable and more cosmopolitan than Homeric warriors. But those warriors are also given space. In recent years the poet Alice Oswald has wonderfully reanimated Homer, turning his catalogues of killings into a grave lamentation for the lost lives of so many young men, while novelists such as Pat Barker and Natalie Haynes have looked past the hypermasculine militarist legend to the plight of the women of Troy.

Martel does something different and interestingly problematic – he acknowledges the dreadful glamour of the masters of war and the thirst for blood without which conflict would be unimaginable. (Harlow remembers his grandfather, who fought in Vietnam, waking from a senile doze to tell him: “We are hiding places for monsters.”) He also, in shifting attention from the supermen to the wretched other ranks, unmasks the sordid misery of battle. The armour that rubs and chafes. The soldier, before a battle, vomiting with fear. The lice and fleas. The teeth spat out “like olive pips” after a blow to the head. The men sobbing in their tents, missing home, missing wives, missing children.

There are exotic animals in this Troy, and animals, as readers of Martel’s Booker-winning Life of Pi know, are numinous beings in his fiction. In place of gods, he gives us giraffes and porcupines and elephants, the last being crucial to a bold variation on the familiar story. Why construct a wooden horse to get inside the city walls, when you have gigantic tusked creatures capable of tearing down the Scaean gate? These beasts introduce a picturesquely sacred dimension to the Psoad, but there is another less successful strand to the work, important both to the fictional Harlow Donne and the real Yann Martel, who has spoken publicly about the centrality of religious faith to his concept of a full life. Harlow suggests that the warrior heroes of the ancient epic “created the space” for the advent of Christianity, “the other half of the profoundly contradictory western character”. The idea is pushed insistently in Harlow’s notes, but Martel fails to make a persuasive case for it, leaving it insecurely tacked on to the exuberantly reimagined pagan material.

Nor does he quite make good his apparent intention to balance the devastation of war against Harlow’s private heartbreak. Harlow explains to little Helen that the Iliad is about angry men who shout and fight. “So it’s like you and Mommy?” asks the child. But no, it really isn’t. Nor is the nervousness of a man about to ask a woman out on a date an adequate equivalent for the terror of a soldier waiting for the command to advance. Son of Nobody is a fine novel, but with an unbalanced structure. Harlow’s voice, in the footnotes, is pernickety and self-pitying – easily eclipsed by Martel’s impressive pastiche of epic mode. Whatever the outcome of the domestic strand, it can’t match up to the blazing horror of the epic story’s ending, with “a rain of children” tossed off the walls of Troy.

• The Scapegoat by Lucy Hughes-Hallett (HarperCollins Publishers, £12.99). To support the Guardian, order your copy at guardianbookshop.com. Delivery charges may apply.

• Son of Nobody by Yann Martel is published by Canongate (£20). To support the Guardian, order your copy at guardianbookshop.com. Delivery charges may apply.