Throughout her childhood Eleanor Roosevelt was desperate for the approval of Theodore Roosevelt. Because her adoring father, Elliott, had died of alcoholism, she leaned on her swashbuckling Uncle Ted for guidance. She relished the way he spoke full-throatedly about North American bird life and read aloud Norse legends. For Eleanor he was the best supercharged citizen to emulate. Until one day, when Uncle Ted explained to his favorite niece that war, for all its horror, could cleanse the soul with patriotic uplift. “I rebelled at the time,” Eleanor later remembered, “and still rebel at the thought that war alone can bring out the best in people.”

As David Michaelis makes clear in “Eleanor” – an excellent single-volume biography of America’s greatest first lady – modest rebellion best encapsulated her paradoxical personality anchored in Victorian morality and cutting-edge feminist bravery. With her toothy smile and genial radiance, utterly void of pretense, Eleanor epitomized grace under pressure, folksy common sense, loyalty to friends and a bedrock belief in American democratic virtues. Her lifelong bully pulpit mission was preserving individual liberty against the European totalitarian model of empowering the state at the citizen’s expense. Although rather shy and polite, she nevertheless became an outstanding orator with an irrefutable fan base. “I have faith in you,” she reassured the American people after the bombing of Pearl Harbor. “I feel as though I was standing upon a rock, and that rock is my faith in my fellow citizens. Whatever is asked of us, I am sure we can accomplish it. We are the free and unconquerable people of the United States of America.”

Nothing about “Eleanor” is staid or plodding. Michaelis, the author of wonderful biographies of Charles Schulz and N.C. Wyeth, writes beautiful nonfiction prose much in the vein of the late Edmund Morris (the great biographer of Theodore Roosevelt). Wherever the intrepid Eleanor travels, Michaelis offers vivid descriptions of topography, wardrobe, weather conditions and societal moods as if an understudy for Charles Dickens. While Michaelis’s style is sometimes florid, his uncanny ability to nail down the atmospherics of a particular place and time with consummate grace is engaging.

When Eleanor married Franklin D. Roosevelt, her fifth cousin, in 1905, their life became consumed with politics and raising children. Social justice causes took a back seat. Whether it was helping her husband grapple with paralytic illness or consoling friends through World War I, first and foremost Eleanor was about aiding others. With exacting detail Michaelis documents her astonishing growth from anti-suffragist opposed to the 19th Amendment to high-profile women’s rights oracle. In 1920 – when FDR ran an unsuccessful bid for the vice presidency – Eleanor joined the Union of Women Voters, just as Congress amended the Constitution and granted women the right to vote. She wrote a stream of articles and bulletins expressing gender consciousness. By 1924 she had become a Democratic Party activist working weekends for the League of Women Voters and raising money for the Women’s City Club of New York. Two years later she created a school for girls. Bursting with energy, indefatigable like her Uncle Ted, the sky was the limit to what she might achieve as a progressive rainmaker. “Eleanor Roosevelt had all her life,” Michaelis believes, “been happiest when she discovered something she could do that she had been told she could not do.”

When FDR ran for governor of New York in 1928, Eleanor mobilized women to vote for her husband and the Democratic presidential nominee, Al Smith. By the time FDR won the presidency in 1932, Eleanor had metamorphized into a compassionate voice for women, minorities and people in need. Instead of wearing expensive clothes, she donned plain and ordinary dresses. Breaking tradition, she became the only first lady to regularly hold news conferences. Her syndicated “My Day” column was ubiquitous. She wrote about politics, self-help, pastoral nature and Christian religion with earnest ease. “Mrs. Roosevelt never lets anybody feel embarrassed in her presence,” an acquaintance of the first lady once explained. “You can do something wrong, but nobody will notice it, because Mrs. Roosevelt covers it up.”

Contrary to popular belief, Eleanor didn’t enjoy being first lady. When Franklin pondered whether to break tradition and run for an unprecedented third term in 1940, she was sickened by the idea. “Eleanor was ready to get on with life after the presidency,” Michaelis writes. “She told (daughter) Anna that if her father didn’t leave the White House in 1941, she would. The prospect of another four years of dividing herself between what she wanted to do and what she had to do held no appeal.” Once FDR won, the cult of Eleanor was as wide as the Mississippi River. African Americans, women, workers and children across the nation were her core constituents.

During World War II the very name Eleanor Roosevelt stood for the Four Freedoms that her husband had put forward in early 1941: freedom of speech and worship, and freedom from want and fear. When Fleet Adm. William F. “Bull” Halsey – stationed in Noumea, New Caledonia – learned that the first lady was making an inspection trip of GIs in Pacific Theater hospitals in August 1943, he was indignant. Deriding Roosevelt a “do-gooder,” he was positive that her goodwill island-hopping tour was a foolhardy stunt. He was wrong. More than 400,000 soldiers delighted in seeing her in person, enchanted by her wit, openheartedness and nonchalant charm. She was treated as a hero of democracy in these far-flung hospital wards. “I was ashamed of my surliness,” Halsey repented. “She alone accomplished more good than any other person or group of civilians who had passed through my area,”

Once FDR died in April 1945 and Eleanor no longer lived at 1600 Pennsylvania Ave., she globetrotted to help displaced people and war refugees be treated with dignity. Elected head of the United Nations Human Rights Commission in London, she helped draft the foundational Universal Declaration of Human Rights. And she initiated the establishment of Americans for Democratic Action, a group focused on domestic social reform and resistance against the Soviet Union and the dangerous Cold War square-off. The last chapters of “Eleanor,” when the Swiss physician David Gurewitsch enters the narrative as a love interest, are absolutely spellbinding.

Eleanor, in both the 1952 and 1956 presidential elections, fought hard for Adlai Stevenson, the Democratic nominee; he lost both contests to Dwight Eisenhower. By the time John Kennedy was president, she in many ways was a 19th-century woman operating in the world of Sputniks and intercontinental missiles (though she enjoyed television, even appearing in a margarine commercial). At the time of her death in 1962, her residences in Manhattan and in Dutchess County, New York, were adorned with unmatched pieces of furniture handed down by great-aunts and distant cousins. Never a public or private showoff, doilies and framed photos of deceased relatives were her notion of decor.

She never tried to be au courant. “I know very little about ‘rock and roll,’ ” she admitted to a record executive when Elvis Presley was the youth rage. “I have seen some of my own young people do it rather conservatively. I would say if the photographs which I have seen are any sample of the way it is usually done, then I must frankly say that … I have found that stirring up pure emotion with very little reason behind it is never a very good thing for young or old.”