As editor in chief of Harper’s Bazaar magazine between 1934 and 1958, Carmel Snow aimed to create a publication for “well-dressed women with well dressed minds.” She became famous for creativity and acumen that drove both circulation numbers and hemlines to previously unknown heights. Over a career that spanned nearly four decades, Snow revolutionized the fashion industry.

Before alcohol took its toll on both her business and social standing, Snow was known to the industry as a firecracker who chaperoned couture into postwar ready-to-wear while securing a place in America’s WASP establishment, an unlikely position for a mid-century Irish-Catholic immigrant.

In “A Dash of Daring” (Atria Books, 576 pages, $29.95), Penelope Rowlands documents how – during her tenure at Harper’s Bazaar, and before, as a fashion editor at Vogue – Snow championed fashion photography as an art form, integrating photojournalistic action shots into her pages. Along the way, Snow encouraged the careers of Cecil Beaton, Henri Cartier-Bresson, Man Ray, Richard Avedon, and Andy Warhol.

She was one of the first editors to feature serious fiction in a women’s fashion magazine, including work by Colette, Katherine Anne Porter, Carson McCullers, and Truman Capote. She also hired the zealous socialite and fashion legend Diana Vreeland, and tirelessly promoted the designers Balenciaga, Givenchy, Saint Laurent, and Dior, among others.

The first half of Ms. Rowlands’s book is fawning hero worship; the author is so enamored of her subject that she fails to imbue Snow with any depth. Snow becomes a one-dimensional mannequin, guiltless and beyond reproach, even when she ditches her mentors at Vogue for its chief competitor.

Only in the second half of the book, when Snow falls victim to the three martini lunch, is she shown to be a complex – and vastly more interesting – modern woman. It is unfortunate that it takes increasingly alcoholic and volatile behavior, including urination on the steps of a Rothschild mansion, to make this character a vulnerable human, more than the sum of her stitches and seams.

Snow’s story is a juicy one, if you can find it among Ms. Rowlands’s purple prose and persistent, abysmal metaphors. Labor pains cause Snow’s formidable mother to “rise up, as majestic as an ocean liner” and she is later described as “a steamroller, if not a Mack truck.” Snow’s predecessor at Harper’s Bazaar is “a domino waiting to fall,” and, worse still, the author compares German Vogue to the Lusitania: “The magazine had begun to list, and then to sink. It would disappear beneath the waves.”

At times, the writing borders on ludicrous, relating Snow’s trajectory to episodes in ancient mythology. Ms. Rowlands likens her subject to Persephone, “drawn back into the underworld” when Snow returns to work at her mother’s dressmaking store. When Conde Nast rescues Snow from this “hell,” he is a “messenger from the gods.” And later, the author calls Snow’s “throne” at the Paris fashion shows “Mount Olympus,” while “lesser gods and goddesses perched on lesser peaks.” Ms. Rowlands’s cliched and melodramatic text needs an editor on par with Carmel Snow.