Some writers have a lucky pen. Others a trusty notebook. Erik Larson has his weird monkey lamps. The pair of matching bronze lamps—each featuring a Capuchin monkey with a mischievous stare—look like props from The Wizard of Oz or a 1940s noir and sit in the office of Larson’s Manhattan apartment, on opposite ends of the wood dining table that serves as his writing desk.

“These lamps are my favorite thing in here,” Larson says over Zoom, patting one of the monkeys. He also has a Stay Puft Marshmallow Man figure and a straw lemur, among other curiosities, that remind him to have fun while working. His daily routine includes eating a Double Stuf Oreo at his desk each morning (“It’s 60 calories I don’t need, but it’s a ritual”) and having drinks when the day wraps. “At five o’clock, I hit a bell on my desk, turn on my Spotify playlist, and have a cocktail—a martini or a Manhattan—with my wife. To me, writing isn’t a job. I love it.”

The bestselling author of nine thrilling books, Larson has a unique power to animate history and make it accessible. His works—which have sold more than 10 million copies, according to his publisher, Crown, and have been translated into 35 languages—include The Devil in the White City, the Edgar Award–winning story of the 1893 Chicago World’s Fair and the serial killer H.H. Holmes; The Splendid and the Vile, about Winston Churchill and London during the Blitz; and his sole work of fiction, the standalone audiobook No One Goes Alone, a ghost story about a 1905 expedition to investigate paranormal activity.

Larson’s latest, The Demon of Unrest, out in April, concerns the five-month period between the election of Abraham Lincoln and the beginning of the Civil War, and focuses on the back-and-forth push between Union and Confederate forces for control of Fort Sumter near Charleston, S.C., which was fired upon by the Confederates in April 1861, igniting the larger conflict.

Larson was inspired to write the book after reading old documents about the run-up to the war. “I went down the rabbit hole and never came out,” he says. “I’ve stated numerous times that I’d never write a book about the Civil War. Well, never say never!”

A page-turner rich with period detail, The Demon of Unrest aims to capture “the ticktock of America’s march toward fratricide,” Larson says, as it delves into the lives of key figures including Maj. Robert Anderson, the beleaguered officer who tried to keep Fort Sumter out of Confederate hands; Mary Boykin Chesnut, a Southern socialite; and Edmund Ruffin, a trigger-happy Virginia slaveholder keen on secession. “My ideal reader is someone who knows little about the Civil War,” Larson adds, “and who’s coming to the book because there’s the promise of a good story.”

To tell the story, Larson dug through archives and private communications and visited the Charleston Historical Society, where he examined fliers advertising slave auctions and bank documents that listed Black people as collateral. “The most important, vivid, and horrifying thing was going though those records,” he recalls. He was struck by the “banality of evil” that permeated Southern life.

He also visited Fort Sumter—now a tourist destination. “I thought it was going to be like the Château d’If in The Count of Monte Cristo, a scary fortress. But it was nothing like the gloomy experience I was hoping for.”

While Larson worked on the book, the Jan. 6, 2021, attack on the U.S. Capital happened—and it left him unsettled. “The past had come to life in an unpleasant way,” he says. “I realized then that this book is very much a story of the present.”

Amanda Cook, Larson’s editor, praises the author for his ability to illuminate history’s biggest moments. “Erik thinks like a novelist even though each sentence is meticulously fact-checked,” Cook says. “He makes great use of primary source materials overlooked by historians. He’s also just a lot of fun.”

Larson’s literary agent David Black—whom Larson calls his “forever mensch”—echoes Cook’s sentiments. “I adore Erik,” he says. “When I read The Demon of Unrest I was transfixed. It’s a kaleidoscopic view of this world and a testament to Erik’s talent.”

Born in Brooklyn in 1954 and raised on Long Island, Larson was a studious kid with a big smile and a flair for drama. “My friends and I used to do chemistry experiments trying to reanimate dead ants,” he remembers. “I spent half my childhood burning sulfur over a Bunsen burner to create smoke for the backdrop for our cap gun play.”

Larson made his first attempt at a novel in junior high—it was inspired by Nancy Drew books and featured a sex scene. After earning a journalism degree from Columbia University in 1978, he wrote for newspapers and magazines and kept pushing to do longer pieces. In 1983, he met his future wife—a doctor with whom he has three daughters—on a blind date, and, after a couple of broken engagements (“I was a classic noncommitting male,” he admits), got married in 1985.

Since the publication of Larson’s first book, The Naked Consumer, in 1992, his wife has been his invaluable first reader who marks up his manuscripts with smiley faces and zzz’s—feedback he relies on. “My wife is exactly the audience I seek for my books,” he says. “This isn’t for scholars; it’s for people who want to come to a world new.”

Larson, a fan of Alfred Hitchcock and Dashiell Hammett, writes with a cinematic touch that has made him popular in Hollywood. Most of his books are in various stages of film and television development, notes Jason Richman, Larson’s agent at United Talent Agency, including No One Goes Alone, which is being made into a movie. “Erik puts everything into his work,” Richman says. “He tells emotional stories set against large backdrops and always takes a human approach.”

When Larson isn’t writing—lately he’s been tinkering with a psychological thriller—he enjoys cooking and checking in on his adult daughters, to whom he sends anxious “dad alerts,” reminding them to stay safe. “The lowest point of dad alerts came after I read about a sea otter attacking a woman and sent a dad alert to avoid otters,” he says.

Larson’s humor and sense of wonder enliven his books and help him to connect readers to the larger world. “I love using real-life material to tell a story,” he says, leaning against his table with the matching monkey lamps. “I want to sink a person into an era, and suspend their knowledge of what happens next.”

Elaine Szewczyk’s writing has appeared in McSweeney’s and other publications. She’s the author of the novel I’m with Stupid.

This article has been updates for clarity.