MARY TODD LINCOLN A Biography By Jean H. Baker Norton. 429 pp. $19.95 THE TRIALS OF MRS. LINCOLN The Harrowing, Never-Before-Told Story of Mary Todd Lincoln's Last and Finest Years By Samuel A. Schreiner Jr. Donald I. Fine. 333 pp. $18.95

MORE BOOKS have been written about Mary Todd Lincoln than any other first lady in American history, with the exception of Eleanor Roosevelt. The Library of Congress card catalogue lists over 20 biographies of Mrs. Lincoln. These include a valuable, if sentimental one by a niece, Katherine Helm, and a substantial one by Ruth Painter Randall. Her letters have been collected by Carl Sandburg and, more comprehensively, by Justin and Linda Levitt Turner. She has been the subject of a novel by Irving Stone, of a Broadway play by James Prideaux and of a book of photographs edited by Lloyd Ostendorf. There are published transcripts of her two trials and innumerable essays analyzing her psyche, character and influence. More than 40,000 items in the Library of Congress Manuscript Division document her life and times in dizzying copiousness.

Clearly, there is something in the personality of Mrs. Abraham Lincoln that captures the imagination. Now two more books have appeared. One by Samuel A. Schreiner Jr. recounts, in particular, Robert Lincoln's unhappy suit which committed his mother to an asylum. The other by Jean Baker, professor of history at Goucher College, is a full-scale biography. Both have new material, and are substantial additions to Lincoln scholarship.

Baker blames "male-oriented history" for the prevailing view of Mary Lincoln as a neurotic shrew. She shows us instead a woman of rare intelligence, sensitivity and drive, whose tragedy was to inhabit the White House in traumatic times and be devastated by the experience.

Mary Todd Lincoln was born into a prosperous Kentucky family of Scottish Presbyterian ancestry on December 13, 1818. Her father, Robert, was a lawyer, banker and businessman. He married twice and sired 15 children. Mary disliked her stepmother, and in adolescence shifted her familial allegiance to two immigrants from France, Monsieur and Madame Mentelle, who ran a rigorous boarding school nearby.

By all accounts she was a star pupil, excelling in history and literature and becoming fluent in French. Academic distinction brought with it a distaste for provincial life, and she began to pine for "a world elsewhere." At first that world was her sister's affluent home in Springfield, Illinois. There, she first caught the eye of a gauche lawyer from the rural working class. "Miss Todd," he said at a cotillion, "I want to dance with you in the worst way." And, according to Mary, he did.

Baker quotes an entrancing image of Lincoln looking like "old Father Jupiter bending down from the clouds to see what's on," while propelling his partner, "a plump baby crane with neck pronated upward."

Physically and socially they were an unlikely pair. He was rail thin, dark and melancholic; she pudgy, chestnut-haired and vital. Their mutual love of politics and abhorrence of slavery, however, forged an ardent meeting of minds. After a lengthy estrangement of mysterious cause, during which Lincoln was "the most miserable man living," the couple married in November 1842. He was 31 and she almost 24.

Mary's previous suitors, including Lincoln's debating opponent, Stephen Douglas, had all been politicians. After refusing one of them she writes, "My hand will never be given where my heart is not," and she meant it. Her love for her husband survived poverty, war, calumny, assassination, the deaths of three out of four sons, exile, physical and mental illness, and trial by jury.

Baker, alone among Mary Lincoln biographers, touches on the real tragedy of her subject's character and life. It was an incurable narcissism. This plain-faced, Kentucky belle, while professing to need only a house, husband and children for happiness, wanted infinitely more. She longed for money, parties and beautiful gowns, low-cut in order to display what a vulgar senator called her "milking apparatus."

FROM THE beginning she pointed Lincoln toward high office so that she might shine in a suitable arena. While protecting him from predatory lawyers and businessmen, she courted those who could advance a political career. "He is to be President of the United States some day," she told a friend early on. "If I had not thought so I would never have married him, for you can see he is not pretty."

Rumor had it in Washington society before the new president's arrival in 1861 that his wife would be an inadequate White House hostess. But Mrs. Lincoln confounded skeptics. She dressed fashionably, set an elegant table, and held her own in conversation with sophisticated men in what was probably the first salon in American history.

Yet, in spite of her diplomatic skills, she was accused of not being true to the Union cause. All the Todd family supported the Confederacy, and this redounded to Mary Lincoln's embarrassment and pain. She worked wholeheartedly in hospitals without ever receiving the recognition she deserved.

Booth's bullet of April 14, 1865, shattered the only world in which Mary Lincoln ever felt fulfilled. "I am bowed to the earth with Sorrow," she grieved. Characteristically, in her 17-year widowhood she identified with Queen Victoria. Dressed in mourning, she haunted European spas, and shopped extravagantly in the hope of moving in aristocratic circles to which she felt a right to belong.

Contrary to the myth that she herself encouraged, Mary Lincoln was not short of money. Lincoln had saved $70,000 of his $100,000 presidential salary, and the interest from his wife's half of this together with a pension of $3,000 provided her with an income of some $6,750 a year. But financial security did not mend her broken heart. "I wish I could forget myself," she said. Being the center of her own universe, she never could.

Baker excels in placing the Lincolns in their historical context. For example, she has illuminating descriptions of the tedium of 19th-century domestic chores and of ignorant medical and gynecological procedures. Yet in an era when women routinely gave birth to eight or 10 children, Mary and her better-educated contemporaries produced an average of three. They accomplished this by the disciplines of abstinence and "truncated practice," by prolonged breast-feeding and by taking abortion potions. Sanitary primitiveness was not as successfully combatted as pregnancy. Fecally contaminated water from the Potomac River was pumped into the White House and probably caused the death from typhoid fever of William, the Lincolns' 11-year-old son.

Mary looked upon the loss of this "sainted" boy as a "personal abandonment." He was the son who most resembled his father in humor, intellect and generosity. On him she had concentrated all her hopes. After his burial, her grief verged on madness, and she turned increasingly to spiritualism and crystal-gazers. Her belief in se'ances was fortified by the knowledge that Empress Euge'nie of France and Queen Victoria were fellow mystics.

Of the 14 photograph in Baker's book, the most poignant shows Mary with a ghostly Lincoln standing behind, his protective, or restraining, hands on her shoulders.

Sylvia Jukes Morris is the author of "Edith Kermit Roosevelt: Portrait of a First Lady." She is working on a biography of Clare Boothe Luce.