One of the most annoying trends in fiction right now is the novel based on the life of a literary figure. What’s the point of trying to fictionalize Virginia Woolf or Zelda Fitzgerald when they’ve already told their own stories in their own distinct voices? In comparison, a lot of 21st-century literary ventriloquism just seems like a pale imitation.

Jami Attenberg’s new novel, Saint Mazie, nearly falls into that category. It’s based on a 1940 New Yorker profile by Joseph Mitchell of Mazie P. Gordon, owner and proprietor of the Venice Theater and self-appointed guardian of the bums of the Bowery. Mitchell’s story is full of details about the hows of Mazie’s particular brand of philanthropy—he follows her through her days holding court in the Venice’s ticket booth and monitoring the goings-on on the block and her nights roaming the streets handing out dimes and bars of soap and physically dragging particularly destitute characters off to flophouses—but he never uncovers the why. Maybe, since he was writing for an audience that was just emerging from the Depression, he didn’t feel it was necessary. For Attenberg, though, it’s a question that’s worth spending an entire book unraveling.

Mitchell’s Mazie is a tough broad with a heart of gold, always on the move, who in the movies would have been played by Mae West. Attenberg’s Mazie tells her own story through diary entries and fragments of an unpublished autobiography. Writing things down gets her thinking. Introspection makes her sadder, less wisecracking than brittle. She tries too hard to sound tough, like a dame singing a torch song. She writes of her sister, who abandons her devoted fiance to become an itinerant dancer: “She had someone who loved her and it didn’t even matter. She threw it all away like it didn’t mean a goddamn thing to her. I want love. I want it, and I can’t have it, and she throws it away.”

She’s also, it turns out, a bit of a poet. “And then I lost you in the move,” she tells her diary, “and it felt like I lost my life. All the things that happened till now, I’m not sure they were real unless I wrote them down.”

At times like these, Mazie can come off as pretentious, or maybe just the creation of a novelist, instead of the street-smart New Yorker she’s purported to be. The incongruity can sometimes be jarring enough to pull you out of the story. But mostly Attenberg pulls off the trick of writing about the past with a modern sensibility without making Mazie come off as a time traveler from the future educating the yokels of the past or succumbing to the (considerable) temptation to rattle off as much 1920s slang as possible.

She’s also smart enough to construct the novel as a collection of found documents and interviews by a young filmmaker named Nadine who’s making a documentary about Mazie, so all the work of revealing expository details—often one of the clumsiest-handled parts of historical fiction—is farmed out to other characters. (Nadine’s interactions with these people form a sly secondary narrative.)

Her biggest trick, though, is to pull out what she promises in the title: a portrait of goodness. Think of all the good people you’ve encountered in fiction. Think of how many of them are saps. If Mazie’s sometimes a bit too insistent that she wants love, damn it!, at least she wants something. She’s an honest-to-goodness good human being.