What Homer or Sophocles might have made of Greece's euro crisis is hard to say, but the way in which their work anticipates the US-led, UK-followed wars of the last decade is a matter on which much ink has been expended recently, with the opening night of Antigone in contemporary dress at the National Theatre coming on the heels of Madeline Miller's Orange-prize win for Song of Achilles. Miller has spoken of being "absolutely" aware of the parallels between Homer's epic of a long war and the situation in Iraq and Afghanistan, while Polly Findlay, the director of Antigone at the National, has compared her eponymous heroine to a suicide bomber. And now another interpretation of the 9/11 wars as Greek myth comes from Joydeep Roy-Bhattacharya with The Watch, a novel set in Afghanistan that has an opening chapter entitled "Antigone".

Sophocles's story of Antigone, who demands her brother's body back after it is decreed that the traitor's corpse be left to rot, is masterfully relocated and updated in this opening chapter. Roy-Bhattacharya's Antigone is an Afghan woman with stumps for legs who uses the palms of her hands to propel herself on a wooden cart from her war-destroyed village to an American army base. Her brother has been killed in an assault on the base, carried out in retaliation for a US drone attack that wiped out almost his entire family; rather than burying the body, the Americans plan to fly it to Kandahar, where it will be televised as a warning to all insurgents. As his corpse putrefies on the base, his sister sits outside in the baking sun, refusing to leave until she is allowed to bury him. So far, so Greek.

The tone shifts in the following chapter, which is set the day before the woman's arrival and features a classics-student-turned-lieutenant whose story moves between gripping descriptions of a firefight in a dust storm and less enthralling memories/hallucinations of his wife, whom he met during a production of Antigone  which allows Roy-Bhattacharya to slip in Sophocles's 9/11-resonant line: "before the flames of war could burn our tower's crown". The movement away from a story that embodies Greek tragedy to one that invokes it dissipates some of the emotional power of the novel. This shift in register is a problem that keeps reappearing throughout the eight chapters of the novel, seven of them told from different viewpoints (the eighth is made up of entries from the journal of the classics-reading lieutenant).

The Watch is at its strongest when the Antigone figure is somewhere in the frame. At first the soldiers are convinced she's a suicide bomber trying to get inside their compound (a clever twist on the Trojan horse story), but the longer she stays outside the more she works her way into their imaginations as a heroic figure. At night she plays the rabab, and if it's slightly silly to imagine that a woman dragging herself for miles across Afghanistan would decide to bring along a stringed instrument, Roy-Bhattacharya earns our indulgence on this point through the soldiers' responses to the music coming at them in the darkness, which form some of the most haunting passages in the book. Just in case we still don't understand the woman's purpose in the novel, one of the soldiers points it out in the final pages: "She gives the place a face."

It might, of course, be a nod to Sophocles's dramatic form, but that's not quite enough justification for the reams and reams of speech that compose a large part of The Watch. Some of it is effective, conveying both stress and camaraderie, exhaustion and adrenaline, but too often the debating soldiers are mouthpieces for differing attitudes to war or simply become tedious. What the novel does best is silent moments  the woman watching the Americans walk out of the base towards her, the lieutenant stepping into the dust storm  but there are long sections between such scenes, filled with chatter. And it's hard not to wonder about those not allowed to speak  we hear from the Tajik translator on the base, but the members of the Afghan National Army who live there are nothing but shadowy mistrusted figures. The absence of Pashtun male voices in a novel about the Afghanistan war is a perplexing decision in a novel that is structured to embrace a multiplicity of voices.

The final page of The Watch sends readers back to the first chapter, re-evaluating what happened there in light of new information. It's hard to return to the beginning without the faint disappointment which accompanies opportunities that remain only half-fulfilled.

 Kamila Shamsie's books include Burnt Shadows.