When Mark Twain opened his mouth, strange things came tumbling out. Things like hoaxes, jokes, yarns, obscenities, and non sequiturs. He had a drawl—his “slow talk,” his mother called it—that made his sentences long and sinuous. One reporter described it as a “little buzz-saw slowly grinding inside a corpse.” Others thought that he sounded drunk.

He loved to talk: to friends, to reporters, to the crowds of adoring fans who filled lecture halls to hear him. He gave famous after-dinner toasts and tossed off witty one-liners that made great copy for the next day’s papers. He could talk all night, preferably with a plentiful supply of cigars and Scotch on hand. He was always bursting with opinions on topics large and small and humming with ideas for new books and new business ventures. He often had trouble sleeping, and drank to numb his nerves. But he never had trouble talking.

He kept talking until the end. In the last years of his life, when he began writing his autobiography, Twain decided to do it mostly by dictation. He sat in bed, with his head propped up on pillows, and riffed and reminisced for hours at a time, while his stenographer took down everything in shorthand. When he was done, he had more than five thousand pages of typescript.

The result is the “Autobiography of Mark Twain,” a monster that has haunted Twain scholars for a hundred years. Its forbidding size and freewheeling structure have puzzled and infuriated generations of researchers who have descended into the archives, hoping to find a finished memoir and instead discovering ten file feet of musings, interspersed with letters and newspaper clippings. Twain insisted that his sprawling memoir not be published until a century after his death, in 1910, so that he could speak freely about everyone and everything. But he couldn’t resist publishing excerpts in the North American Review before he died. And, in the decades since, more has trickled out as editors have waded through Twain’s papers to uncover pieces that they considered worth publishing.

No complete version appeared until 2010, the centennial of Twain’s death, when the University of California Press published the first of a projected three volumes. The book wasn’t intended for a general audience. It included nearly two hundred pages of endnotes, a scholarly introduction, and a large collection of Twain’s preliminary attempts at autobiography. Even so, the “Autobiography of Mark Twain: Volume 1” sold more than half a million copies. Twain would have been proud. A veteran self-promoter, he had engineered a masterful publicity coup from beyond the grave.

Although the first volume sold well, it received some surprisingly hostile reviews. On the cover of the New York Times Book Review, Garrison Keillor called the book “a ragbag of scraps” and a “powerful argument for writers’ burning their papers.” Adam Gopnik judged it a “disjointed and largely baffling bore” in The New Yorker. And, in the Washington Post, Jonathan Yardley wrote that he felt “trapped in a locked room” with “a garrulous old coot … who loves the sound of his own voice and hasn’t the slightest inclination to turn it off.” It’s easy to imagine Twain enjoying this. To be scolded by critics and embraced by ordinary readers was a familiar experience for him. The general public recognized his brilliance long before the literary experts of his day, and, while he sometimes craved critical approval, he loved to defy and provoke the establishment whenever possible.

Now the second installment of his autobiography has arrived, and it’s unlikely to convert anyone who disliked the first. The book begins where the previous volume left off, consisting of dictations from April, 1906, to February, 1907. Its style is the same as that of the first: Twain pursues whatever chain of thought presents itself, and he continues to pursue it until he gets bored. Other autobiographies “patiently and dutifully follow a planned and undivergent course,” he declares early on. His own, by contrast, is “a pleasure excursion.” It “sidetracks itself anywhere that there is a circus, or a fresh excitement of any kind, and seldom waits until the show is over, but packs up and goes on again as soon as a fresher one is advertised.”

This technique has been a main feature of Twain’s writing from the start. He “wrote as he thought, and as all men think, without sequence, without an eye to what went before or should come after,” said his close friend and his greatest critic, William Dean Howells. This stream-of-consciousness style came partly from his love for the spoken word. He grew up listening to tall tales and slave stories, and he tried to give his writing the slangy spontaneity of speech.

The result was a kind of “continuous incoherence,” to borrow Howell’s phrase, that let Twain realize the rich literary potential of the American vernacular. He helped to create a literature of ordinary life, making art out of material long considered too trivial or too crude to be taken seriously by the custodians of so-called serious culture. In his autobiography, the rambling flow that has always infused his work liberates itself of any pretense of plot or structure and achieves its purest form. It doesn’t always make for riveting reading, but it shows us what made Twain a revolutionary writer.

If you surrender yourself to the sound of his voice, the pleasure of Twain’s company proves pretty hard to resist. His narrative may be loose, but at least it never loses sight of its subject. “This autobiography of mine is a mirror, and I am looking at myself in it all the time,” he declares. Mostly, he likes what he sees. By the time he starts dictating his autobiography, he is a world-famous celebrity and isn’t shy about admitting how much he enjoys his success. He doesn’t try to disguise the satisfaction that he feels when a few of his old letters are sold at auction and fetch a higher price than letters by Theodore Roosevelt and Abraham Lincoln. Journalists hound him for interviews; people recognize him on the street. When he gives a talk at Barnard, a “sweet creature” cozies up to him and coos in his ear, “How do you like being the belle of New York?” “It was so true, and so gratifying, that it crimsoned me with blushes, and I could make no reply,” he writes.

Twain’s vanity, and the undertow of irony that cushions it, makes his autobiography feel especially current. Ironic narcissism is more or less our national default mode now, but Twain was ahead of his time. He was one of America’s first modern celebrities, an icon of the first age of mass media that emerged in the decades following the Civil War. He cannily cultivated his public image—giving interviews, posing for photographs—to become a pop-culture favorite. He found a way to be ambitious and cocky without losing his sense of humor, and thus forged a persona that made people root for him. This character is on frequent display in these pages, and he recalls the narrator of Twain’s nonfiction works “The Innocents Abroad,” “Roughing It,” and “Life on the Mississippi.” By the time he began dictating his autobiography, at age seventy, Twain had perfected the art of self-presentation. He is careful about what he chooses to reveal. “I have thought of fifteen hundred or two thousand incidents in my life which I am ashamed of, but I have not gotten one of them to consent to go on paper yet,” he admits.