Anna Burns won the Man Booker Prize on Tuesday for her novel “Milkman,” which is narrated by an unnamed 18-year-old girl living in 1970s Northern Ireland who is coerced into a relationship with a mysterious older married man with ties to a paramilitary group.

The Booker’s judges cited Ms. Burns’s use of dark humor to explore weighty themes like the perils of tribalism, state-sponsored terrorism, social division and the ways that sexual and political oppression often overlap.

“None of us had ever read anything like this before,” the writer and philosopher Kwame Anthony Appiah, chair of this year’s judges, said in a statement. “It is a story of brutality, sexual encroachment and resistance threaded with mordant humor.”

The novel unfolds in an unnamed city during “the Troubles,” a prolonged civil conflict in Northern Ireland that gave rise to sectarian violence and guerrilla warfare. Against the background of this turbulent epoch, with the constant threat of car bombs and riots, the narrator deals with a menacing stalker, who is known only as Milkman, though he doesn’t deliver milk.