And yet, for all this collective guilt, much of the emotional drive in The Death of a President comes from a simple sense that a big man has been killed by a little one, a king cut down by a serf. Camelot imagery for the Kennedy years sprang not from Manchester but from Theodore H. White (with a conscious assist from Jackie Kennedy). Nonetheless, The Death of a President has enough of its own royalist trappings and machinery to have put off some who read it in manuscript. The main divisions of the text are organized under the characters’ Secret Service code names—JFK is “Lancer,” while Mrs. Kennedy is “Lace”—and the murder happens because the protagonists must make a kind of royal progress, waving from their carriage in all their sexual glamour, through the inhospitable province where some of their vassals have been feuding. The warring factions and egos within the Texas Democratic party thus hasten the end of a “dazzling three-year reign” whose closing moments take place against a backdrop decidedly unfit for a king and queen. The author winces in describing “the automotive nature of the landscape” (too many gas stations) and even “the tawdry Hertz clock” above the Texas School Book Depository. (Never mind that the Hertz rental-car business may have been made possible in part by the president’s father, who during the 1920s manipulated stock in the Yellow Cab Company with his friend John Hertz.)

Manchester tells us that John F. Kennedy, whose “great heart continued to pump” against all odds in the emergency room, was a reader not only of Thucydides but also, when aboard Air Force One, the Bible: “On flights alone the President had read it evenings before snapping off the night light.” Perhaps he did. But a plaster sainthood hardens very quickly around JFK once he ceases to propel Manchester’s narrative with his own words and deeds.

With Mrs. Kennedy, it’s a different story. Manchester may hymn the First Lady’s looks and elegance, but in her he has a living—indeed, suddenly metamorphosing—creature to deal with. After the killing, immune to Scotch and sedatives, she marshals her will for a series of history-minded decisions and truly graceful gestures (gently touching the ham hand of the weeping Sergeant Dugger, for one). Manchester makes plain that Bobby Kennedy, not his sister-in-law, took the initial steps toward planning the massive state funeral. But once Mrs. Kennedy rose to full function, the two of them became a formidable team.

In 1966 they united against Manchester, attempting to thwart serialization of The Death of a President in Look magazine, and then to block publication of the book itself by redeeming the author’s early, unwise promise of “manuscript approval.” In Mrs. Kennedy’s case, Manchester realized, the basic problem was that “she didn’t really want any book” at all on the assassination, especially one that had been enabled by her long, daiquiri-driven interviews with the author. When she met with Manchester to hash things out, she deployed “tears, grimaces, and whispery cries of ‘Jesus Christ!’,” as well as a threatening reminder that the only thing the American public wouldn’t put up with from her was running off with Eddie Fisher.

Bobby Kennedy’s objections followed a political calculus that now seems obscure. Not yet having decided to run for president, he was afraid that Manchester’s depictions of Lyndon Johnson—first as a humbled vice president and then, suddenly, an overeager chief executive—might create problems for himself inside the Democratic party. Evan Thomas, Manchester’s editor at Harper & Row (and father of RFK’s subsequent biographer), proposed a bundle of cuts and changes, not only to please the Kennedy family but to keep Harper & Row from losing a crack at LBC’s own memoirs when the time came for them to be auctioned.

Thomas Mallon is a frequent contributor to The New Yorker, The Atlantic, and many other magazines, and the author of seven novels and six works of nonfiction.