The language, so weirdly puffed up and perfumed, seems almost a form of grief, some strange, Pentecostal utterance that’s the opposite of what poor Sergeant Dugger was suffering. Metaphors are either baffling (“as obvious as a Parcheesi board”) or tormented through extension, and the tone can be crazily uncertain, as in one passage where Manchester twists himself into a combination of Cotton Mather and Mickey Spillane. He is attempting to explain why the tony New Frontiersmen could never have understood the sleazy world of Jack Ruby, Oswald’s killer:

The men and women who had surrounded President Kennedy . . . were unacquainted with the maggoty half-world of dockets and flesh-peddlers, of furtive men with mud-colored faces and bottle blondes whose high-arched overplucked eyebrows give their flat glittering eyes a perpetually startled expression. . . .

During his battle with Bobby and Jackie Kennedy, Manchester’s editors would betray him in the largest way possible, sticking up for the writer’s subjects instead of the writer. But they also let him down line by un-blue-penciled line.

When The Death of a President was released in 1967, public confidence in the Warren Report was only beginning its long slide down the Grassy Knoll. Manchester dismissed the possibility of conspiracy in the space of two footnotes. His contempt and anger toward Oswald are so keen that he can barely allow the assassin onto the page. To the author, Kennedy’s killer is a head case (“he was going mad”) whose Marxist politics are too puerile for consideration, and who can be dismissed as “barely literate.” In fact, though painfully dyslexic, Oswald was a serious reader whose library borrowings in the summer of 1963 included Manchester’s Portrait of a President.

Manchester remains, then, what students of the assassination call an LN (Lone Nutter), as opposed to a CT (Conspiracy Theorist). However, he belonged to a large liberal sect of Lone Nutterism that believed a citywide atmosphere of political malice had prodded Oswald toward his explosion. Dallas, with its fiercely right-wing ethos, is more or less made into the killer’s codefendant.

Over and over, the author suggests what he calls “a plural responsibility for the tragedy,” and quotes others who spoke in the same vein. Ralph Dungan, a special assistant to President Kennedy, remarked that “the hell of it is, they’ll blame it all on that twenty-four-year-old boy,” while David Brinkley declared on network television, as JFK’s coffin was lowered into the ground, that “the act which killed the president was spawned out of bigotry and extremism.” The city’s tendencies toward both were marked. That they led Lee Harvey Oswald to kill John F. Kennedy—seven months after he nearly succeeded in killing General Edwin Walker, the most celebrated right-wing extremist in Dallas—is no more clear today than it was in 1967. Nor is it any clearer now whether the myriad cheering spectators for Kennedy’s Dallas motorcade should assume or escape a share of the “plural responsibility.”

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.

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.