“The Great Deluge: Hurricane Katrina, New Orleans, and the Mississippi Gulf Coast” (William Morrow, 736 pages, $29.95) is the historian Douglas Brinkley’s bid for literary and historical greatness. Hoping to follow in the footsteps of David McCullough, whose fine book on the Johnstown flood established his sterling historical reputation, Mr. Brinkley has sought to create an instant epic, parlaying the story of Hurricane Katrina’s rampage through the Gulf Coast into a natural and human drama of cosmic scale. This massive book, based mainly on journalistic sources and the author’s own interviews, and crammed with an immense amount of detail, is the result.

One can be excused for wondering from the outset whether enough time has passed for anything of this epic scale to be written about these tragic and infuriating events – or whether Mr. Brinkley is the man for the job. Let me confess that I haven’t read all of the writings of Douglas Brinkley. I doubt that anyone – perhaps not even Mr. Brinkley himself – has ever done that. He is a veritable … deluge of literary productivity, with books to his credit on a dizzying array of subjects, ranging from Beat poetry to Jimmy Carter, and from Henry Ford to, most recently, the failed Democratic presidential candidate John Kerry. Indeed, the range of his literary productions is so wide as to seem indiscriminate. But his best-known writings seem to have three things in common.

First and foremost is their relentless mediocrity. I cannot think of a historian or public intellectual who has managed to make himself so prominent in American public life without having put forward a single memorable idea, a single original analysis, or a single lapidary phrase – let alone without publishing a book that has had any discernable impact. Mr. Brinkley is, to use Daniel Boorstin’s famous words, a historian famous for being well-known.

Second is their sloppiness, partly an inevitable product of the haste in their composition, and partly, one suspects, of a mind that becomes easily bored by careful, close analysis. Mr. Brinkley’s views may always track the conventional wisdom, but you would never want to rely on his books as sources of accurate detail. Would you trust a writer who trades on his intimate knowledge of the Gulf South, and yet claims at one point (page 548) that a tired-looking President Bush could not have been jetlagged because “Washington was in the same time zone as Mobile”?

Third, and perhaps most important, is their political agenda, although the word “political” does not quite do the matter justice. Better to say that Brinkley always seems to be seeking someone’s favor in what he writes.Which is to say that he has the moral instincts of a court historian. And this means that the would-be patron holds the key to the book’s real meaning.

In the case of the Kerry biography, that was easy enough to detect. In the case of “The Great Deluge,” Mr. Brinkley seems to have three things in mind. First, he clearly is trying to intervene in the New Orleans mayoral race, and more generally in the politics of Louisiana. “The Great Deluge” is notable for its astoundingly nasty and cartoonish treatment of New Orleans Mayor C. Ray Nagin, and its near-hagiographical treatment of Mr. Nagin’s electoral rival, Mitch Landrieu – an account whose most colorful stories rely heavily on interviews with such objective sources as … Mitch Landrieu. As before with John Kerry, so now with Mr. Landrieu, Mr. Brinkley has not done the careful, time-consuming work of testing the veracity of his sources.

More generally, the book attempts a concerted (but completely unconvincing) effort to redeem the reputation of Louisiana Governor Kathleen Blanco, whose failure as a leader was at least as conspicuous as Mr. Nagin’s. But Ms.Blanco represents the Louisiana Democratic political establishment whose corrupt and incompetent leadership of the state over many decades had far more to do with the calamities of Katrina than Mr. Nagin’s failures of leadership and tactics. Although Mr. Brinkley mentions, in passing, that Mr. Nagin had supported Ms. Blanco’s Republican opponent, Bobby Jindal, he does not mention the ugly use of racial innuendos against Mr. Jindal, a dark-skinned South Asian, to help Ms. Blanco win the election. He includes just enough criticism of Ms. Blanco to save himself from the charge of puffery, but puffery is, in fact, what he is about.

Which leads to the third purpose. Mr. Brinkley claims, without anything like sufficient evidence, that the White House and Republican leadership allowed policy to be dictated by naked partisanship, since they saw in Katrina an opportunity to discredit the current leadership,and thereby make Louisiana a Republican state,once and for all.This is a serious charge, but Brinkley’s most convincing evidence is the fact that Ms. Blanco herself claimed this was so.

One should add, too, that there is no serious criticism of the astounding malfeasances of the news media in covering this story. No mention of the hysterical falsehoods about bodies stacked in freezers and gunfights in the Superdome that were put out to the world,and that have stuck in the world’s mind, even as their basis in fact crumbled. Instead, Mr. Brinkley writes about the news media exactly as you would expect someone who wants to be well treated by them, and invited back to appear on their cable shows: They were all heroes.

All of this would be forgivable if Mr. Brinkley had written a book that was lively and evocative. But “The Great Deluge” turns out to be a book worthy of its title. It just goes on and on and on, a veritable Mississippi of sludgy, sophomoric, rebarbative prose, with gimmicky human-interest stories, transcriptions of press releases, gratuitous quotations from great writers about hurricanes, and potted history. This author may feel the gravity of his subject, but he does not manage to convey it.

Here, to give you a sample of his prose, is the way Mr. Brinkley describes the scene at the crowded Louisiana Superdome: “Scanning the sweep of the Superdome on Tuesday evening, watching the suffering and confusion, one became acutely aware that ‘the blues’ was not all boodlie-bum-bum on Bourbon Street.” Such is the eloquence of this instant epic.

Mr. McClay teaches history and humanities at the University of Tennessee at Chattanooga.