Imagine Charles Dickens, his sentimentality in check but his journalistic eyes wide open, roaming New Orleans after it was buried by Hurricane Katrina. He would find anger and pathos. A dark fable, perhaps. His villains would be evil and incompetent, even without Heckuva-Job-Brownie. In the end, though, he would not be able to constrain himself; his outrage might overwhelm the tale.

In “Zeitoun,” what Dave Eggers has found in the Katrina mud is the full-fleshed story of a single family, and in telling that story he hits larger targets with more punch than those who have already attacked the thematic and historic giants of this disaster. It’s the stuff of great narrative nonfiction.

Eggers, the boy wonder of good intentions, has given us 21st-­century Dickensian storytelling — which is to say, a character­-driven potboiler with a point. But here’s the real trick: He does it without any writerly triple-lutzes or winks of post­modern irony. There are no rants against President Bush, no cheap shots at the authorities who let this city drown. He does it the old-fashioned way: with show-not-tell prose, in the most restrained of voices.

In that sense, “Zeitoun” has less in common with Eggers’s breakthrough memoir, “A Heartbreaking Work of Staggering Genius” (which met with mostly deserved trumpet-blaring in 2000), than it does with his 2006 novel “What Is the What,” the so-called fictionalized memoir of a real-life refugee of the Sudanese civil war. In that book, Eggers’s voice took a back seat to his protagonist’s outsize story. But it was an odd hybrid.