Alex Wong / Getty Warren Buffett

Correction Appended: Sept 8, 2009

By masterminding Tuesday's $5 billion investment in Goldman Sachs, Warren Buffett showed he still has the touch that has won him plaudits as the world's greatest investor. But a new biography, which will hit bookstores Sept. 29, reveals that in his personal life, the Oracle of Omaha can be something of a wreck.

The Snowball: Warren Buffett and the Business of Life was written by Alice Schroeder, a onetime insurance-industry analyst who agreed at Buffett's request to chronicle his life. It's the first biography with which Buffett, 78, has cooperated.

Buffett, the book reveals, isn't always the calm, calculating figure we know as head of the storied investment firm Berkshire Hathaway. He could be an emotionally needy husband and an absentee father, a man who purposely avoids people he fears might criticize him.

Although Buffett revered his father, a stockbroker who became a four-term Congressman, he had a complex relationship with his mother. A model housewife to the outside world, his mother would "verbally lash" the young Buffett and his older sister for hours, until the children wept. Buffett says that when his mother died he cried not because he was sad but "because of the waste. She had her good parts, but the bad parts kept me from having a relationship with her."

Schroeder writes at length about the women who would later fill the void and care for Buffett. Primary among them was his wife of 52 years, Susie. During their early years together, settled into family life with their three children in Omaha, Neb., Buffett worked voraciously; Susie "knew that the main thing he needed was to feel loved and never criticized." In public, people noticed how affectionate the two were  Warren liked to hold Susie in his lap  but in private, his wife kept hoping that once they had enough money (between $8 million and $10 million, she figured), Buffett would cut back on work and finally pay attention to his family. What she didn't realize was that the mission Buffett had embarked upon when he was 6 years old and selling gum and Coke to his neighbors would never stop. The quest to amass wealth  but not to spend it, as his license plate, THRIFTY, suggested  would take him all the way to being the richest man in the world.

Once the kids were grown and gone, Susie decided to move out and left for San Francisco. She and Warren lived apart for 27 years, and while they still talked extensively by phone, he was crushed by what he considered the biggest mistake of his life. "He wandered aimlessly around the house, barely able to feed and clothe himself," writes Schroeder. For a while, Susie thought she'd have to go back, but in the end she asked Astrid Menks, a restaurant hostess and sommelier she knew, to check up on her husband. Eventually, Astrid moved in. "Susie put me together, and Astrid keeps me together," was how Buffett came to explain things. After Susie's death in 2004, Warren and Astrid got married.

There were other women keeping Buffett on track while "he ruled out paying attention to almost anything but business." There was Sharon Osberg, the bridge player who first persuaded Buffett to use a computer  a task even his good friend Bill Gates couldn't pull off. There was Carol Loomis, the writer at Fortune (which, like TIME, is owned by Time Inc.), who edited Buffett's annual letter to shareholders. And, most vividly depicted of all, there was Katharine Graham, the publisher of the Washington Post, in which Buffett was a major investor. Graham became Buffett's entrée into high society (the man of notoriously simple tastes once said he had an easier time talking to Dolly Parton than to Princess Di), and Buffett became Graham's tutor in the ways of business. With Graham, Buffett the protected became Buffett the protector.

The book, to be sure, recounts Buffett's remarkable accomplishments as a businessman. And it affirms the image of Buffett as a peculiarly American success story, the multibillionaire (Forbes just estimated his worth at nearly $50 billion) with an aw-shucks aura. There is the Buffett who insists on carrying his own luggage even when flying by private jet. The Buffett who as a teenager got C's and D's in school and stole golf equipment from Sears, yet also filed his first tax return, for $7, deducting his wristwatch and bicycle as expenses in his newspaper-delivery business. And there is the Buffett who desperately craves attention and gets excited when a porn star says on her website that he's her hero. Buffett, Schroeder writes, is "at heart nothing more than a starstruck little kid, endearingly clueless in many ways about his place in the pantheon."

Most riveting is the portrait Schroeder paints of the family's dealing with Susie's oral cancer. Buffett, who always expected his wife to outlive him, reels from the news. He is terrified of losing her and cries for hours. Buffett had always avoided hospitals and was squeamish about all things medical  a "man who ducked the subject of a common cold and used terms like 'not feeling up to par' as euphemisms for illness; the man who changed the subject uneasily whenever anyone spoke of physical complaints." And yet with his wife undergoing radiation after facial surgery, he overcomes his limitations, learns everything he can about oncology and sits by her bedside weekend after weekend in San Francisco, watching with her nearly 100 episodes of Frasier. When Susie can eat only a liquid diet, Warren cuts his own intake to 1,000 calories a day. "That can't be a lot of fun," he says, "so I won't have any fun either."

And yet when Susie eventually does die, Buffett can't cope. As his daughter, also named Susie, is planning the funeral, she tells him he doesn't have to attend. "Warren was overcome with relief," Schroeder writes. " 'I can't,' he said. To sit there, overwhelmed with thoughts of Susie, in front of everyone, was too much. 'I can't go.' "

There are some challenges even the world's greatest investor can't handle.

The original version of this article stated that Fortune magazine writer Carol Loomis writes Warren Buffett's annual letter to shareholders. Loomis in fact edits the letter.

See photos of The Berkshire Hathaway Annual Shareholders Meeting.