Alas, Manchester’s overwriting—as inadvertent as Tom Wolfe’s was deliberate—can reach grotesque extremes. Trapped in their limousine amid the gunfire, Oswald’s victims “lay entangled in their abbatoir.” The assassin didn’t kill, he “slew,” while a cigarette that’s being smoked is seen “shrinking to its doom.” If another book has ever made multiple uses of the word “debouched,” I’ve yet to read it. The diction throws up one risible roadblock after another: “apopemptic,” “comminated,” “vermiculating,” “atrabilious.” Maybe all this helped me with my sats back in 1967, but in 2009 I find myself skipping to the next paragraph instead of reaching for a dictionary.

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.”

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.