In 1927, 15-year-old Edward Robb Ellis bet two friends to see who could keep a diary the longest. One boy petered out after two weeks; another kept daily entries for three months before calling it quits. Ellis, on the other hand, was still writing his diary in 1995 — 24,000 days and 20 million words after that teenage wager — earning him a spot in the Guinness Book of World Records. About 1 percent of that diary has been distilled into the one-volume A Diary of the Century, first published in 1995, three years before the author’s death. The reissue doesn’t offer any new material; but what’s here remains a multicolored mural of American life across seven decades. In his introduction Pete Hamill writes, “The diarist has one essential goal: to freeze time.” Ellis does that with gusto and an obsessive compulsion for detail. Each of his entries is like a flashbulb popping on an American timeline: bank failures during the Great Depression; Louis Armstrong blowing his trumpet in a New Orleans jazz club; a stunned Grace Kelly emerging from an elevator to face a pack of reporters; an execution at Sing Sing; and thousands of other memorable moments. As a reporter in the Midwest and New York City, Ellis seems to have been everywhere and rubbed elbows with history’s who’s who. Browsing the names in the index, you realize Ellis is the Forrest Gump of diarists. Robustly sentimental and splashed with an inevitable egocentrism, this diary is as close to being there as most of us will ever get.