They called each other “darling,” “dear one” and “heart.” They told each other “je t’aime” and “j’adore,” and wrote more than 3,000 letters to one another.

“All day I’ve thought of you . . . Oh! I want to put my arms around you, I ache to hold you close,” the normally reserved Eleanor Roosevelt wrote in March 1933 to her beloved. No, not her husband, President Franklin Delano Roosevelt, but a brilliant, bourbon-drinking, cigarette-smoking Associated Press reporter named Lorena Hickok, or Hick.

Their romance is at the center of Susan Quinn’s engrossing double biography, “Eleanor and Hick: The Love Affair That Shaped a First Lady.”

While Quinn is not the first to tell the tale of Eleanor and Hick, she brings new depth to their epic, three-decade-long love story.

Quinn’s book begins in 1932, shortly before Hick began covering Eleanor Roosevelt during FDR’s presidential campaign. “THE DAME HAS ENORMOUS DIGNITY, SHE’S A PERSON,” she wired her boss, after observing Eleanor’s unease with the spotlight at that year’s Democratic convention.

Hick spent the following weeks as “Eleanor’s appendage,” Quinn writes, traveling on the campaign trail and earning her trust. (Eleanor told Hick that she “never wanted to be a president’s wife, and I don’t want it now.”)

By the time FDR was inaugurated in 1933, the two women had fallen in love. The evening before FDR delivered his famous line about having nothing to fear but “fear itself,” Eleanor read it to her girlfriend. Hick had a singular scoop — the president’s first speech — but out of loyalty to the first lady, she let it go.

As for the president, he accepted his wife’s friendship with Hick (he had his own extramarital affairs). Hick even got her own room at the White House to be closer to Eleanor.

Not one to show physical affection, even to her children, Eleanor showered it upon Hick, describing the tender kisses she wanted to give her when they were apart.

Hick responded with equal passion: “I’ve been trying to bring back your face,” she once wrote, recalling “the feeling of that soft spot just north-east of the corner of your mouth against my lips.”

With Hick by her side, Eleanor learned how to navigate the press. Her popular newspaper column “My Day” grew out of the diary that she had been sending Hick in letter form and ran from 1935 to 1962.

Paradoxically, Hick’s relationship with the Roosevelts forced her to abandon her career as a news reporter. But because of Eleanor, she got a job working as a field investigator for Harry Hopkins, the head of New Deal relief programs. Her vivid and poignant dispatches from the poorest parts of the country influenced the government’s efforts and President Roosevelt himself.

‘All day I’ve thought of you . . . Oh! I want to put my arms around you, I ache to hold you close.’ - Eleanor Roosevelt to Lorena Hickok

Eleanor and Hick made a solid team, but they weren’t without their troubles. Hick resented Eleanor’s endless appointments and family entanglements.

“Above all, Hick was a writer,” Quinn concludes. “But she couldn’t seem to sell her work. Part of the problem was her loyalty to the Roosevelts: All her pieces about them lacked critical distance.”

Hick sacrificed that distance for closeness to Eleanor, whose affections later shifted toward her handsome, much younger doctor, David Gurewitsch. “I love you as . . . I have never loved anyone else,” Eleanor wrote him in 1956.

After Eleanor’s death in 1962, Hick lived for 5½ more years, worn down by blindness, arthritis and loneliness. She finally died of complications from diabetes at the age of 75.

With great ceremony, Eleanor was buried alongside Franklin at the Roosevelts’ Hyde Park estate in upstate New York; in addition to the ambassador to the United Nations and two former presidents, Harry Truman and Dwight Eisenhower, President John Kennedy attended her funeral, where she was remembered as “the First Lady of the World.”

In her anonymity, Hick was cremated. Her ashes sat on a shelf of a funeral home for 20 years before being interred in an unmarked grave at a cemetery in Rhinebeck.

Brooke Hauser is the author of “Enter Helen: The Invention of Helen Gurley Brown and the Rise of the Modern Single Woman.”