Barack Obama Sr. married four times, but the most important woman in his sadly troubled life was a middle-aged American literacy teacher, Elizabeth “Betty” Mooney, who hired the young Kenyan as her Nairobi secretary in 1958 and soon sponsored — and helped fund — his dream of attending college in the United States.

Obama flew to the U.S. not as part of a larger student airlift, as is generally believed, but only because Mooney mentored his admission to the University of Hawaii and persuaded fellow literacy advocate Frank Laubach to help defray Obama’s expenses. This significant discovery is just one of many notable revelations in Sally Jacobs’s “The Other Barack,” but the cumulative effect of her thoroughly researched biography is deeply depressing. Jacobs, a reporter for the Boston Globe, has far outstretched all previous journalists in unearthing an impressive array of new information about Obama’s life, but her richly sourced account of how a promising young adulthood quickly descended into daily alcoholic binges and serial domestic violence paints an even more dramatically downbeat portrait than did Obama’s namesake son 16 years ago in “Dreams From My Father.” Indeed, although “The Other Barack” greatly enriches our knowledge of the elder Obama’s life, it is such a painfully disheartening narrative that some interested readers — and certainly one in particular — should avoid Jacobs’s tragic account.

When Obama flew to Hawaii in August 1959, he left behind a young Kenyan wife already pregnant with their second child. At the university, he pursued a demanding course load and a highly active social life. In the fall of his second year, hardly six weeks elapsed before one new female classmate, 17-year-old Stanley Ann Dunham, became pregnant with their child. The university’s foreign student adviser told U.S. immigration agents, who took an active interest in foreign students whose visas required annual renewal, that she already had cautioned the married Kenyan about his dating habits. When Obama informed her in April 1961 that he and Dunham had married two months earlier, Obama also asserted that he had divorced his Kenyan wife. The adviser told the immigration agency she was dubious of that claim, but that Obama had told her that “although they were married they do not live together and Miss Dunham is making arrangements with the Salvation Army to give the baby away.” That sentence is redacted in the copy of Obama’s immigration file viewable on the Web, but Jacobs, working from a differently processed version, is unable to fully capture the emotional impact of the memos’ tale of ongoing official enmity.

Given Obama’s seeming lack of interest in parenting his offspring, adoption may have appealed to him, but no other evidence suggests that Ann Dunham actually considered giving her firstborn child away. Within weeks of Barack Jr.’s birth, Dunham and the baby left Honolulu for her previous home town of Seattle, leaving behind the husband with whom she had never lived. When Obama prepared a resume just before leaving Hawaii for graduate school at Harvard in 1962, he listed “a wife and two children in Kenya,” Jacobs reports. “He made no mention of Dunham or Barack Jr.”

Obama’s admission to Harvard’s PhD program in economics attested to his academic success in Hawaii, but once again his freewheeling personal life attracted official criticism. A Unitarian minister complained to U. S. immigration that Obama was intimately involved with a young Kenyan woman attending a Boston-area high school, and after two years, Harvard’s international student adviser told immigration agents that the university did not want Obama’s visa to be extended for a third year. Obama had passed the examinations qualifying him to begin writing his dissertation, but Harvard’s action — expressly motivated by animus toward his personal conduct, and with no academic rationale — forced the visibly upset graduate student to return to Kenya with only a master’s degree.

'The Other Barack' by Sally H. Jacobs (PublicAffairs. 297 pp. $27.99)

Within weeks of Obama’s departure for Nairobi, his newest girlfriend, 27-year-old Ruth Baker, got on a plane to follow him. They married four months later, and the following year Ruth met Obama’s first wife, Kezia, in a Nairobi hospital after their husband’s drunken driving left a young friend dead and Obama with two broken legs.

Ruth Obama Ndesandjo is the book’s most compelling and memorable source; the stories of her life with Obama describe nothing less than a living hell. “He was a man I had a very strong passion for,” she told Jacobs, but “The Other Barack” narrates a series of increasingly violent drunken assaults that culminated with Obama putting a knife to her neck. “I did not think he would really kill me. He was a bluffer,” Ruth explained. She realized that at her husband’s core, “he had a great, enormous insecurity” that nothing except endless amounts of whiskey could medicate. Only when Obama struck one of their two young sons did she finally leave him.

Obama stumbled in and out of several mid-rank government jobs before killing himself in his umpteenth drunken car crash in November 1982. By then he was living with a fourth wife, or wife-to-be, a 20-year-old woman who had given birth to his youngest child six months earlier. The great promise and energy that Betty Mooney had seen in him a quarter-century earlier was long spent. But had white antipathy toward his unrestrained personal life not shattered Obama’s life dream of a Harvard PhD, whiskey might not have derailed a brilliant alcoholic from a life of far greater length and achievement.

Garrow, a senior fellow at Homerton College, University of Cambridge, is the author of “Bearing the Cross,” a Pulitzer Prize-winning biography of Martin Luther King Jr.