Epitaph, Mary Doria Russell’s new book about the gunfight at the O.K. Corral, might almost be a called a nonfiction novel, like In Cold Blood. The gunfight story is as overlaid with myth as anything that ever came out of the Old West (for starters, it didn’t take place at the O.K. Corral), but it was the subject of extensive investigations and hearings in the period after it occurred. Russell draws on studies that have unearthed these, and Epitaph is dense with actual events to a startling degree.

Only the most minor characters aren’t real, and the dentist Doc Holliday, the subject of an earlier Russell novel, is fleshed out here in more detail. In Epitaph you can learn a great deal about anything from restaurant menus in Tombstone to the political divisions in post-Civil War America. “A deeply divided nation. Vicious politics …” runs the blurb. “A president scorned by half the public. Smuggling and gang warfare along the Mexican border. Armed citizens willing to stand their ground and take the law into their own hands. That was America in 1881.”

But Russell’s cleverest investigative technique is to embed the story of the O.K. Corral myth itself into her own true story. The gunfight, which lasted only thirty seconds, takes place about two-thirds of the way through the book; the rest traces the later career of U.S. Marshal Wyatt Earp and those who began to profit from embellishing his story. Tales that were long taken as fact, including the fictionalized memoir I Married Wyatt Earp, purportedly by his widow Josephine Earp but now thought to be a hoax, are worked into the narrative, which ends only in 1945 with Josephine’s death.

Beyond the realm of nonfiction are the characters, their thoughts and motivations explored in convincing, down-to-earth ways. Compared with all the earlier legendary American figures who have taken up this story, from John Ford to Larry McMurtry to Robert Parker, Russell’s contribution is to focus on the women in the story. Central among these is Josephine, the daughter of a Prussian Jewish baker who took his family around Cape Horn from New York to San Francisco. Her early life and her escape into the world of vaudeville, which brought her to Arizona and eventually to Wyatt Earp, take up much of the first part of the book.

Russell talks about the gunfight at the O.K. Corral–and Epitaph–at the Kerrytown Book Festival on September 13. It should be a fascinating look at where real life leaves off and fiction begins.