At times, “The Long Walk,’’ Brian Castner’s memoir of his work disarming bombs in Iraq and his turbulent reentry into civilian life, is almost unbearable to read. Not because the writing is bad — it’s often excellent. It’s unbearable because of Castner’s brutally vivid descriptions of the war and the way it tore apart his mind and his life.

An officer in the US Air Force, Castner was deployed twice to Iraq, in 2005 and 2006, to lead a team charged with taking apart IEDs — the improvised explosive devices that have caused so much mayhem during the war. Castner describes heading out to scenes of carnage in Kirkuk and other cities, often multiple times a day, feeling the “tentacled hate” of the crowd surrounding the soldiers while they rush to collect evidence and defuse any unexploded ordnance.

"The Long Walk" by Brian Castner

If team members are lucky, they can send a robot out to do the work. If not, one of them has to face the “long walk”: heading out alone onto a hostile street in an 80-pound Kevlar suit, perhaps watched by the person who put the bomb there in the first place. “There is no more direct confrontation of wills between bomber and . . . technician than the Long Walk,” Castner writes. “Donning the suit, leaving behind rifle and security, to outwit your opponent nose to nose.”

Castner comes home from the war physically unscathed. But mentally he falls victim to what he comes to call “the Crazy.” This affliction is with him all day — when he wakes up, when he drives his kids to school, when he lies in bed next to his wife. She at one point begs him to cheat on her so that she can feel freed to take their four sons and leave him. “I can’t follow you into this dark place,” she tells him. The only way he can tamp down the Crazy is to go for punishing runs. And while he can remember with precision nightmarish details of what he saw and did in Iraq, he can no longer remember things like the births of his children. In crowded places such as airports or grocery stores, he finds himself selecting the people he needs to kill in order to escape.

Castner eventually learns he is suffering from blast-induced traumatic brain injury, or TBI — similar in ways to what befalls some football or hockey players after repeated concussions — and that his memory and personality have been permanently altered by his proximity to countless explosions. He makes it painfully clear how much of himself he has lost. “I died in Iraq. The old me left for Iraq and never came home. . . . I liked the old me, the one who played guitar, and laughed at dumb movies, and loved to read for days on end. That me died from a thousand blasts. Died covered in children’s blood. Died staring down my rifle barrel, a helpless woman in the crosshairs and my finger on the trigger. That me is gone. . . . The new me has a blown-up Swiss-cheese brain, and doesn’t remember all of the old me. But it remembers enough. Enough to be ashamed.”

Writing about “The Long Walk’’ makes Castner’s story sound much more linear than it is. In reality, the book jumps and loops around incessantly, mirroring Castner’s disordered mind. Clearly the scattered style is purposeful — though maybe, too, it’s the only way Castner could have put his story on paper. But at times the disjointedness undercuts the power of the narrative by making it very difficult to follow.

Still, this is an important book to read for anyone who wants to get some sense of the long-term human toll of the Iraq war. How many soldiers have been damaged as Castner has? How many lives and families have been destroyed — or will be — by the effects of TBI? “The Long Walk’’ brings home in a visceral way the hidden, personal burden of war that many veterans continue to carry.