At the height of the Iraq War, David Finkel, a reporter for the Washington Post, embedded himself with a US infantry battalion in Baghdad and wrote an acclaimed book called The Good Soldiers. Then he followed the men home and watched many slip into a vortex of violence, despair and suicide. The result is Thank You for Your Service, a stunningly intimate portrayal of young veterans and their families haunted by a soul-corroding legacy of combat.

Finkel weaves his book around a series of soldiers afflicted by the uncontrollable rage, nightmares and disorientation of post-traumatic stress disorder (PTSD). Two people in particular anchor the narrative: Adam Schumann, a tough sergeant from Kansas who suffered a breakdown during his third tour of Iraq; and Saskia, his wife, who is driven to the edge herself by a daily battle to shore up their disintegrating marriage while caring for their baby son Jaxson and six-year-old daughter Zoe.

The force of the book lies in the sheer amount of time Finkel has spent with the Schumanns and his other subjects, whose quarrels, tears and rare moments of redemption he frequently witnesses. Finkel has diced his mountain of reportage into a sparse prose style reinforced by meticulously observed details and snatches of dialogue (including Saskia and Adam’s routine rows by text message). The effect is to create an experience more akin to watching a documentary than reading a book. It can be excruciating. Adam, distracted and exhausted, drops Jaxson; the couple trade painful barbs during a car ride to one of Adam’s hospital appointments; Saskia begs him not to shoot as he points a shotgun at his forehead.

As the couple’s crisis deepens, Adam’s memories of Iraq crystallise. A soldier was shot in the head and he hoisted him onto his back; he can still taste the man’s blood flowing into his mouth, staining his teeth. Adam suffers even worse torment from the guilt he feels over the death of James Doster, who was killed in a blast on a patrol he had missed. Another soldier tells him that Doster would still be alive if Adam had been there with them: ‘None of this shit would have happened if you were there.’ He meant it as a compliment: Adam was the sharpest-eyed bomb spotter they had. But Adam heard an accusation and ‘nailed it into his soul as blame’.

Doster’s widow Amanda is also cast in a leading role as Finkel captures her years of grief. At first she smiles and says, ‘Hi, James’ to the box containing his ashes. Three years on, she is no longer seeing James behind the wheel of a pest-control truck, but she might have recently spotted him on TV.

Flashbacks to the men’s experiences in Iraq convey the realities of devastating roadside-bomb attacks and sniper fire. But the little details of casual brutality are perhaps more telling: US troops throw dollar bills to Iraqi kids to provoke fights and bet on the outcomes; a sergeant notices a piece of a dying soldier skidding across the floor of an aid station and pronounces, ‘That’s a toe.’ The last words Schumann hears from any of the soldiers he fought with, as he is about to be medevacked for his PTSD, carry an undertow of contempt: ‘Well, I’ll walk you as far as the shitters, because I have to go to the bathroom.’

While the US has spent billions of dollars to care for the flood of physically and psychologically wounded from Iraq and Afghanistan, facilities can have a dehumanising feel. In one centre, psychiatric patients earn privileges for good behaviour like inmates in a prison. Greater solace is on offer at a privately run rehabilitation centre in California, where Adam eventually finds some peace.

Finkel explores the epidemic of suicides in the US military by chronicling a campaign by General Peter Chiarelli, the US Army vice chief of staff, to stem the tide of self-harm. In a book comprised almost entirely of memorable scenes, Chiarelli’s macabre video conference with commanders stationed around the globe in which they dissect the latest hangings and shootings is among the most chilling. Chiarelli, who commanded troops in Iraq, is clearly committed to his mission, but the vast scale of the task makes his piecemeal measures seem almost futile.

In a rare respite from the harrowing realities of war, Finkel manages to open an ingenious window onto the world of Washington lobbying by eavesdropping on an aide and a chef discussing the menu for a dinner Chiarelli plans to host for senators. They bicker over pistachio sea bass with frisée and warm bacon vinaigrette, only for senators to start cancelling anyway. Finkel wonders if the topic of suicide prevention put them off.

The wars in Iraq and Afghanistan are history now to most people in America, as they are in Britain. David Finkel has shown their true meaning for the soldiers who fought them and those they love.