President Roosevelt didn't think much of ''Gone With the Wind.'' ''No book,'' he said, ''needs to be that long.'' He was in a minority, of course. That too-long Civil War novel has sold 6 million hardback copies in the United States, 1 million in England, and 9 million in translation, outselling any other hard-cover book except the Bible. It inspired so many souvenirs, tourist attractions, and paperback rights, plus, of course, the movie, that it has become as much an industry as a book.
Its author, Margaret Mitchell Marsh, as her biographer makes clear, was no stereotyped Southern blossom - but then how could she be, since stereotypes don't exist in real life and individuals can't be pigeonholed? She was tiny (under 5 feet tall), a feisty rebel, a tomboy child nicknamed ''Jimmy,'' whose suffragist mother encouraged her to wear an old pair of her brother's pants.
In her Road to Tara (Ticknor & Fields, $15.95), Anne Edwards makes a good job of the story of complicated adult Margaret Mitchell, who thought she could be both an outrageous, outspoken product of the jazz age and an acceptable member of Atlanta society. She fell in love with an Ashley Wilkes-like character, then married and divorced a Rhett Butler. Her second husband, John Marsh, who spotted the potential of the embryo ''Gone With the Wind,'' was the man '' . . . without whom this book would never have been written.'' She longed to be a successful writer, but publicity terrified her. She became incredibly rich but always felt poor.
She insisted that she never intended the book to be published, but went to enormous trouble to check every historical detail. And when she finally agreed to let an editor see it, her manuscript (if that's the right word for it) consisted of 2,000 pages stuffed into envelopes, including 60 versions of the first chapter.
In fact, there's a hunk of the fictional Scarlett O'Hara in the real-life Margaret Mitchell, just as there's a hunk of the career of ''Gone With the Wind'' in ''Road to Tara.'' And it's this secondary biography that I find the most fascinating.
Anne Edwards shows how the seeds for Margaret's obsession with the Confederacy were sown in her childhood, when Sunday afternoons were spent listening to veterans refighting the battles of the Civil War and to women reliving the burning and looting of Atlanta. Not all of them were old enough to have been there - but they remembered all the same. When she was 4, Margaret entertained a Sunday gathering with her rendition of ''I'm a Good Old Rebel.''
That same year Margaret was taken to Atlanta's traditional April 26 parade, and the grip of the Confederacy tightened its hold.
''Georgians had come from every corner of the state. . . . There were no balloons, shouts, or cheers, as at other parades. First came a band playing Confederate songs; then the artillery and artillerymen sitting on the caissons, their arms crossed; then the infantry and cavalry. As they marched by, people would shout, 'Hello, Bill!' and 'Hello, Joe!' But when the band stopped playing, a sudden hush swept through the spectators. No one moved, as marchers held high a great mass of blood-red flags emblazoned with white stars. Shuffling along behind was a long line of old men, survivors of the great war. These were Atlanta's soldiers, the men who had fought their cause.''
And so the atmosphere of the 1860s became home to Margaret Mitchell. And it wasn't until she was 10 that Margaret learned what the rest of the world had known for 40 years: The South had lost the war.
Don't read this book to find out if Margaret Mitchell meant Scarlett and Rhett to get together again. Her biographer doesn't know. But she does answer, to my satisfaction, at least, the question as to why ''Gone With the Wind'' was so successful. It was a rattling good story, of course - but 6 million in the US alone?
Anne Edwards points out that timing had a lot to do with it. In 1936 a country suffering the effects of the depression needed a Scarlett O'Hara to remind it to refuse to be ''blown away by the winds of change.'' In fact, tough times keep drawing in new readers whose gumption is brushed up by Scarlett's vow: ''As God is my witness . . . I'm going to live through this, and when it's over, I'm never going to be hungry again.''