IN AND OUT OF VOGUE: A MEMOIR By Grace Mirabella Doubleday 257 pp., $25 When Grace Mirabella was ousted from her 17-year post as the editor in chief of Vogue magazine in 1988, book publishers quickly offered her deals. After all, who better to detail what she deemed the rather ''unstylish'' way she found out she was fired from the fashion magazine (word came first from a television newscast) and to chronicle the goings on in the fashion industry for the past four decades. That Rupert Murdoch subsequently helped her launch a new magazine - named Mirabella - also made her story golden. This week, not only is Mirabella's magazine returning to newsstands for the first time since it was sold by Murdoch in the spring, but her autobiography is also finally gracing stores. ''In and Out of Vogue: A Memoir,'' written with the help of Judith Warner, is a readable look at a world that we ''civilians'' - as we're called by fashion-industry insiders - rarely get to see. From the post-World War II rise of ready-to-wear to the birth of runway shows in the late 1970s, readers get the skinny on the author and the industry. Founded in 1892 as a ''journal of society, fashion, and the ceremonial side of life,'' Vogue hardly seemed the place for a New Jersey native and the shy daughter of Italian immigrants. But through connections she landed a post-college job at the chichi magazine in the '50s, and became its editor in chief in 1971. Despite some challenges to her leadership (because she wasn't a ''flamboyant fashion type'' or socialite), Mirabella's no-nonsense philosophy prevailed: clothes for real-life women. She brought in writers like Susan Sontag and Calvin Trillin, and replaced the psychedelia and go-go boots of the '60s with clothes for American women entering the workplace: those by Bill Blass, Geoffrey Beene, Calvin Klein, Ralph Lauren. Circulation skyrocketed from 400,000 in 1971 to 1.2 million by 1988 when she was let go. She resisted cigarette advertising and making Vogue more like its new youthful competitor, Elle, ultimately getting fired, she thinks, for the latter.