In Marcel Theroux’s postcollapse ­novel, “Far North,” global warming has reduced civilization to largely pre­industrial levels of technology and made sparsely populated areas like the Siberian tundra safer than lawless cities. There’s a satisfying sadness and finality to Theroux’s vision, but the story’s true power comes from the hard-won victories of its remarkable narrator, Makepeace. “A person is always better than a book,” Makepeace claims, and the novel’s enduring achievement is to give us a protagonist who lives up to that claim.

Face scarred by violence, Makepeace patrols the streets of deserted Evangeline, a Siberian town founded by Quakers. After mistakenly shooting a Chinese boy named Ping and then nursing him back to health, Makepeace learns that Ping has a secret — and it’s the same secret harbored by Makepeace herself. Ping is a woman, disguised as a man to fool a violent world. In Ping’s case, she’s also trying to disguise her pregnancy.

Theroux is never shy about subverting expectations. Soon after Ping recovers, Makepeace says with typical yet heartbreaking understatement, “I can’t dwell on what happened next, . . . but in June, Ping died and the baby died with her.” Ping’s death serves as a kind of turning point for Makepeace: it will kill her or force her to engage the world.

Then she witnesses a plane crash, and her despair turns to curiosity: Is the plane a sign of returning civilization? During Makepeace’s quest for the answer, members of a strange cult take her prisoner and sell her to slavers. The detail that destroys her is the same one that destroys the reader: “Sometimes, when you’ve suffered a lot, it turns out to be the small thing that breaks you. That chain almost finished me.”