This powerful novel, which is on the short list for next month's Hemingway Foundation award, might never had existed if a publisher hadn't read a 2013 BuzzFeed story about Walker's experience as a medic in Iraq and his tragic aftermath.
He contacted Walker, then serving an 11-year sentence for bank robbery (he's scheduled for release next year) and Cherry - a novel a world away from the usual "written in my creative writing class" doggerel that passes for modern American literary fiction - is the result.
Cherry perfectly captures the bewilderment of a new Lost Generation
Walker enlisted in the army at 19, served with distinction as a medic in Iraq in 2005 and 2006, and returned with PTSD and a burgeoning drug habit.
One critic described the prose as "like a good conversation in a dark bar between adults drunk enough to not care about censoring themselves".
Rarely has self-loathing read so well or been so funny.
It doesn't help that the girl he falls in love with, the inscrutable Emily, will only serve to bring him down further.
That masochistic streak helps explain why this vegetarian hipster volunteered for service in the first place.
His military training in Texas is a joke - "were the outcomes of all the wars decided by push-ups and idle talk, America might never lose"; when he's in Iraq his medic kit has little more than a few aspirin inside.
His fellow soldiers cope with the absurdity as best they can, torturing mice, smuggling in pills and weed, shooting dogs and beating up "hajis".
"People kept dying: in ones and twos, no heroes, no battles. Nothing. We were just the help, the glorified scarecrows: just there to look busy, up and down the road, expensive as f**ck, dumber than shit".
Walker stayed awake for days just to avoid dreaming the scenes he writes about here - and they are splendid.
If those chapters are a searing indictment on the insanity of war, his homecoming is no celebration. In the States he faces another - America's opioid crisis.
Soon he's hanging around with a revolving band of Cleveland low-lives and a troubled, now ex-wife, Emily who's also addicted.
The robberies - one of which starts the book (after the obligatory overdose) - were crazy schemes - as much about reliving the daily life and death thrill he got kicking in doors in Iraq, as about any real need.
Cherry perfectly captures the bewilderment of a new Lost Generation, one brought up on "high-fructose corn syrup and plenty of television; our bodies... full of pus; our brains skittered"; here in brazen, no-apology prose Bush's absurd war gets the chronicler it deserves.
(Jonathan Cape $37.00)