Humans have colonized the backwater planet Umayma. For reasons that aren't clear, two main factions, Nasheen and Chenja, are at war and pretty much everyone able-bodied gets sent to the Front (except for a few specialists and other exceptions). Nasheen is run by women since men over the age of sixteen or so get sent to Front and very few make it to forty to come back. Chenja seems to keep back a few men to run things but otherwise it's pretty much the same story.
Nyx spent time at the Front and is now a bel dame, a kind of government-sanctioned bounty hunter (as opposed to a regular bounty hunter that isn't employed by the government) who hunts down deserters from the Front among others but she spends some of her time as a regular bounty hunter and gets involved in some illegal stuff that gets her sent to prison. Oh yeah, and she's supposed to cut off her target's head as proof, so I'm guessing that's what's supposed to be wrapped in the bundle she's cradling on the cover.
It's definitely gritty.