On her last book tour, Amy Stewart served specialty cocktails at her readings. It was only fitting for her book, “The Drunken Botanist,” a historical tour of boozy plants. That was Stewart’s fifth work of nonfiction; since 2001 she’s been hitting bestseller lists with her quirky tales of the natural world with books that include “Wicked Plants” and “Flower Confidential.”

“We had so much fun,” she says of that tour. But it was something of a farewell — for now, she’s leaving nonfiction and gardens behind for an unexpected jaunt through Paterson, N.J., circa 1915.

Stewart had become obsessed with the long-forgotten tale of the real-life Kopp sisters. A century ago, when women hadn’t earned the right to vote, Constance, Norma and Fleurette stood up to one of the city’s wealthiest men and his violent gang of thugs.

“I felt this very powerful sense of obligation,” Stewart says. “Everyone forgot about them, and I found them. I dug them up. I resurrected this story, and I can’t not tell it now.”

The Kopps are the stars of Stewart’s new zippy, winsome novel, “Girl Waits With Gun” (Houghton Mifflin Harcourt; 416 pages, $27). Filled with historical detail without being weighed down by it, the novel is a cinematic story of the women, the siege instigated by their powerful enemy, and their brave efforts in the face of real violence.

To fill in the gaps, Stewart wanted the tools available to a novelist; the book is told from Constance’s point of view. She’s the eldest, tall and solid. After their mother’s death, it falls to Constance to preserve the family farm. Her sister Norma is capable and dour, a strong agrarian with a flock of carrier pigeons. Fleurette, the youngest, is a petite proto-flapper who would be flirty if only her sisters let her get into town once in a while.

But taking a trip into town is exactly what caused them to cross paths with the local factory owner, and then their troubles began. Using the threat of the notorious Black Hand, his thugs stake out their house, break windows, shoot at the sisters and threaten to kidnap Fleurette and sell her into slavery. Unlike most who’d suffered similarly, the Kopps allied with authorities to try to prosecute them. The book’s title comes from a headline about Constance, who showed up to meet extortionists not with the promised cash but with a handgun.

“What I wanted was for other people to have the same emotion I had when I found them … ” Stewart says, “that sense of fun and spirit and adventure.”