When Peter Guralnick released Last Train to Memphis, the first half of his superb two-volume biography of Elvis Presley, some people must have wondered, “Who needs two books to tell the story of Elvis?” They may as well have grumbled, “Two whole books about America?” Some lives, some careers, push outward and up, expanding until they burst that flimsy constraint we call a frame of reference.

In 1933, Barbara Stanwyck defied the Hays Office, that huffy watchdog of our movie-going morals, with a performance that might have been shocking if it weren’t so dazzling in its cold practicality. In Baby Face, Stanwyck’s Lily Powers, an oppressed young woman decidedly from the other side of the tracks, watches her abusive father die in a fire — and almost smiles. She heads to the big city, where she sleeps her way to the top tier of a sky-high financial institution. That’s how Lily gets everything she thinks she wants out of life, but Stanwyck’s performance — grounded, vital, more hardscrabble than salacious — offers something beyond vicarious thrills. It gets to the core of wanting so much out of life — a Depression-era life, or any other. No morality code could constrain it. Who was Barbara Stanwyck? And is she one book’s worth of woman, or two?

In A Life of Barbara Stanwyck: Steel-True 1907–1940 (Simon & Schuster, $40), Victoria Wilson covers only the first half of Stanwyck’s story: The book ends just before America enters the Second World War, long before Stanwyck’s days as matriarch Victoria Barkley on the ’60s television show The Big Valley (which is how most under-sixty youngsters first came to know her), and even before her turn as a cool-as-platinum cardsharp in Preston Sturges’s unassailably perfect 1941 romantic comedy The Lady Eve. But Steel-True is so good, so alert to every meaningful detail, that even toward the end of its some 1,000 pages, its gears don’t grind down. It’s a part one that’s already reaching out toward its part two.

Steel-True works the way all good biographies do, as a mini-history of the world around a person. The woman who became Barbara Stanwyck was born Ruby Stevens in 1907 Brooklyn, the youngest in a family of five. When Ruby was four, her mother died of complications following a trolley-car accident; her father deserted the family not long after. Ruby idolized her older sister Millie, a chorus girl who traveled the country and, when she was able, took Ruby with her. So it isn’t surprising that Ruby herself became a hoofer in her mid-teens, eventually breaking into the Ziegfeld Follies. At one point, Ruby and a friend were performing twice a night at theaters a block away from each other in Times Square. “After a few evenings of doing both shows Ruby and Mae had the run figured out,” Wilson writes. “They finished their numbers at the Shubert Theatre, got out of their costumes, threw on their coats… [and] ran out into the cold winter nights and down Forty-Fourth Street wearing nothing but a coat and a pair of shoes.” At the next club, they’d perform their routines, strip out of their costumes, put their coats back on, and rush back to the Shubert in time for their next number.

This is a pointillist book: Wilson, a vice-president and senior editor at Alfred A. Knopf, builds her story detail by detail, and while some of the dots may not seem so important by themselves, their shifting colors settle into place as the chapters roll by. Wilson shows a deft touch in conveying the texture of Stanwyck’s first, troubled marriage to Frank Fay, a gregarious, charismatic entertainer now best known — if he’s known at all — as the onetime husband of Barbara Stanwyck. Fay was at first generous in helping Stanwyck build her career. But he was also controlling and a hard drinker, keeping even the flinty Stanwyck under his thumb until, worn down by beatings and fearing for the safety of the couple’s adopted child, Dion, she fled.

Stanwyck’s second marriage, to ’30s matinee idol Robert Taylor, was much more harmonious, but even then, Stanwyck — who hadn’t gone beyond the eighth grade but who read several books a week, then passing them along to her employees — put more stock in work than in love. From 1930 to 1939, she appeared in 33 films, including several (The Miracle Woman, The Bitter Tea of General Yen) with the young Frank Capra. Capra was deeply in love with Stanwyck, but she was devoted to Fay and refused to return his affections.

Contract disputes, on-set injuries (Stanwyck, it appears, often worked in, and through, pain), ups and downs with the fickle audiences of the ’30s: Wilson covers it all, and if she can maintain the steadfast magic of this first volume (the whole project, thus far, has taken fifteen years), by the time she has completed the second, all of those little dots will form as complete a picture of the headstrong, generous, mysterious Stanwyck as we’re likely to get.