Edward Robb Ellis is “America’s greatest diarist” only by the standards of The Guinness Book of World Records, which has honored Ellis for the 20-million-plus words of the journal he began keeping in 1927 and still adds to daily. Admirable as Ellis’ feat may be, it’s not immediately clear why anyone would want to read the results. On the surface, A Diary of the Century: Tales From America’s Greatest Diarist doesn’t have a lot going for it: Ellis is not a brilliant writer or an original historical thinker. Ellis pithily summed up his own situation on Aug. 24, 1936, when he wrote, “I am neither witty nor clever, I’m just sincere.”

Yet these words are as much a recommendation as a caveat, for the depth of Ellis’ sincerity makes his diary an oddly compelling and sometimes grandly entertaining piece of writing. Born in Kewanee, Ill., Ellis grew up poor in his divorced mother’s home. He developed a passion for reading, and at 16, he suggested a contest among his friends to see who could keep a diary the longest. His only real challenger gave out after three months, and Ellis’ devotion to daily self-reflection soon lent him a reputation as an eccentric. The tenacity with which he recorded his own life struck his family and friends as arrogant, and Ellis reports that they harbored a certain disdain for his book.

In reading the first hundred pages, it’s tempting to agree with them that Ellis could have left well enough alone. The preoccupations of his youth—girls, an after-school job as a movie-house usher, attempts to memorize Spanish verbs—are standard coming-of-age fare, and the writing in these early entries is too clumsy. A 1932 description of a romantic encounter reads like an uneasy mix of police report and dime-store romance: “This evening, she let me kiss her repeatedly, almost causing me to swoon in ecstasy. Her lips are so soft, so moist, so delicious.” The gee-whiz tone grates, and Ellis talks more about keeping a diary than about his life. Eventually, though, his journal-keeping becomes less an affectation than a habit.

Ellis left home when the Depression hit. His hunger for experience and willingness to cede center stage made him uncannily suited to a career in journalism: He worked as a reporter in New Orleans, Oklahoma City, and Peoria before settling, in 1947, into a job with the New York World-Telegram & Sun. The diary charts Ellis’ increasing confidence and skill; the book’s broad midsection, which recounts Ellis’ adventures as a daily reporter, moves with the clarity and lightness of a good feature story. One of the deep pleasures the book affords is a glimpse of a now-defunct, personal journalistic style. Ellis’ news stories, many of which are included here, combine a palpable enthusiasm with respect for their subjects; the result is a good-naturedness that seems naive compared with today’s cautious and arid front pages.

The range of Ellis’ subjects is astounding. He watched Huey Long stump in 1934; traded jokes with Paul Robeson and spent the afternoon with a painfully unfunny Mae West in 1947; watched a pompadoured Roy Cohn grill suspected communists in 1953; attended a birthday party for a cranky 87-year-old Judge Learned Hand in 1959; helped a barely literate Jimmy Durante fill in his marriage license form in 1960; spent an intoxicating 10 minutes one afternoon in 1956 following Greta Garbo down 52nd Street, noting with the heart of a fan and the eye of a reporter the pattern on her skirt, the smallness of her feet, the “crinkled silk” of her aging skin, and the bounce of the white package dangling from a string in her right hand.

Although these pages are studded with powerful and glamorous names, celebrities are not Ellis’ focus. His promiscuous curiosity makes him a consummate egalitarian: He is equally thrilled to spend an afternoon in a rented boat with two 12-year-old boys he met in Central Park (July 5, 1960) or to interview Nixon nemesis Alger Hiss (July 9, 1975). To both encounters he brings an almost religious sense of event, and the incidents are accorded equal space in his diary.

In Ellis’ anecdote about the rowboat, he notes the way the children call the goldfish “goldies,” watches their city-kid awkwardness with the boat’s paddles, listens to and records faithfully their worries. One of the boys, encouraged by the unexpected interest from a stranger, confesses suddenly that “he hates his brothers because they are so lazy they won’t even look for jobs although their mother works very hard at keeping their home clean, that he wants to amount to something, that maybe he’d like to be a history teacher, that he could hardly wait until he became 16 so he might get a job, that his father earns $190 by holding down two full-time jobs.” As usual, Ellis listens hard; he is startlingly attentive to the specificity of the child’s complaint.

It is with the same instinct for detail that Ellis notes that Hiss has “ears with edges as thin as the rims of shells,” that Hiss takes the subway in summer because he doesn’t mind heat, that Hiss is courteous when the waiter keeps forgetting to bring his iced tea, that Hiss at 70 gets tired climbing the five stories to visit his son. (“I must point out that since I was working for the Oral History Collection [of Columbia University], I cannot reveal in this book what Hiss told me on tape,” Ellis adds in an aside. “….However, there is nothing unethical about reporting my impressions of Hiss the man.”)

Ellis does not attempt complex psychological analyses of his subjects. Instead, he concentrates on externals—their bodies, their dress, their manner and turns of phrase—and renders surprisingly compelling portraits. Ellis is aware that what people call the meaning in their lives is the accumulation of unremarkable data. His strategy is simply to collect the mundanities and stand by as they take on shades of significance.

This is the technique of a human-interest writer, and A Diary of the Century is a tribute to a reporter’s willingness to find hints of high drama in the most ordinary existences. In the end, of course, it is Ellis’ own story that’s told most eloquently. The diary proceeds at a leisurely rhythm, but remains absorbing even after Ellis leaves his newspaper job to write about history full-time. Ellis—who culled the entries himself—is forthcoming about his drinking habit, his loneliness, and the pain of his unsuccessful first marriage. He shares the euphoria of marrying his second wife, Ruth Kraus, in 1955, and his unexpected happiness over the following decade. Ruth dies of a heart attack in 1965, and Ellis carries his grief with him through the long final third of his life. He struggles with an increasingly dingy and dangerous New York.

But he never gives in to maudlin reminiscence or retreats into his imagination. Even as the tone of the entries grows more contemplative, the diary is borne up by the strong current of its author’s interest in the world. At 84, when death looms “like a ship emerging from the fog,” Ellis remains eager to go people-watching at a nearby Barnes & Noble or strike up a conversation with the man who sleeps on his street corner. He maintains his hard-nosed lucidity, and the result is a book that reaches far beyond one man’s life.

Ellis lived through several of the most treasured, ridiculed, and painful moments of the 20th century. Simply by having been there, Ellis lends a concrete emotional weight to the clichés Americans use to talk about their nation’s history. The Edward Ellis who wore his press card in his fedora in the ’30s is the same Edward Ellis who emerged from years of hard drinking to attend AA meetings in the late ’60s. The man who listed “Sophisticated Lady” as one of his favorite songs in 1934 is the same man who turned on to marijuana in the ’70s, shook his fist at Lifestyles of the Rich and Famous in the ’80s, and trembled with shame at the video-recorded brutality of Los Angeles police in the ’90s. There is courage in such longevity, and A Diary of the Century stands as a deeply humane document of 68 difficult years.