HILIP ROTH is one of America's great novelists, but you don't expect him to be barreling up the best-seller list with a book that hasn't even been published yet. "Literary fiction," as it is now stigmatized in the cultural marketplace, no longer flies off the shelves unless struck by the TV lightning of Oprah or the "Today" show. And yet there was "The Plot Against America" in the top 25 at amazon.com this week, at one point the only serious contemporary American novel on the list, sandwiched between Clay Aiken's memoir and "The South Beach Diet." It ascended without benefit of a single author's interview on TV or anywhere else and with only the first few reviews, not all of them ecstatic.

Since the book isn't officially published until Oct. 5, online shoppers are quite literally judging it by its cover image, a one-cent stamp of the 1930's crisply postmarked with a swastika, and the bare bones of its story. The plot of "The Plot" belongs to a low-rent genre, "alternate history," in which novelists of Mr. Roth's stature rarely dwell. It spins a what-if scenario in which the isolationist and anti-Semitic hero Charles Lindbergh runs for president as a Republican in 1940 and defeats F.D.R. "Keep America Out of the Jewish War" reads a button worn by Lindbergh partisans rallying at Madison Square Garden. And so he does: he signs nonaggression pacts with Germany and Japan that will keep America at peace while the rest of the world, six million European Jews included, burns.

Where "The Plot Against America" fits into the hierarchy of Mr. Roth's canon, which I and so many others have followed for our entire reading lifetimes, may be beside the point over the short haul. Sometimes the public, acting on instinct, just picks up the scent of something it craves without regard for the aesthetic niceties. Whether it's major or minor Roth, this novel is on a trajectory to match the much-different "Portnoy's Complaint" in its anomalous permeation of the larger culture. That's because "The Plot Against America," set from 1940-1942, is on its face linked to the wartime of 2001-2004. It's going to be read by those who don't otherwise read Roth novels, or novels at all, as well as by those who do. Not for nothing does it sit on a best-seller list dominated, low carbs notwithstanding, by a single subject, George W. Bush.

The book is riveting from the very first sentence: "Fear presides over these memories, a perpetual fear." That fear belongs to the Newark Jewish family to whom its history happens, among them its principal narrator, the 9-year-old "Philip Roth," his parents and an inevitable Aunt Evelyn, who is so besotted by celebrity and power that she happily kicks up her heels at a White House state dinner for the Nazi foreign minister, Joachim von Ribbentrop. But the fear you feel is not so much that the Roths and their neighbors are going to face mass murder at the hands of a fascist American government. Nor, conversely, do you believe they are going to be able to prevent the fate of the Jews of Europe. No one can rewrite that history, and we know from the start that Mr. Roth wouldn't be so silly as to try. What grabs us instead is the sinking sense that the "perpetual fear" he describes is in some way a cousin to the fear we live with now. Surely "perpetual fear" defines our post-9/11 world - and the ruthless election-year politics of autumn 2004 - as succinctly as what Mr. Roth tagged "the ecstasy of sanctimony" defined the Monica summer of 1998, in which he set "The Human Stain."

In an essay in Sunday's New York Times Book Review, Mr. Roth took a swipe at President Bush ("a man unfit to run a hardware store let alone a nation like this one") but not before saying that he conceived this book in December 2000, and that it would be "a mistake" to read it "as a roman ý clef to the present moment in America." He's right. It can't be. Yet it's precisely because "The Plot Against America" wasn't written to make facile analogies between then and now that the light it casts on this present American moment seems so illuminating. Literature still can accomplish what nonfiction and ideologues can't. By sweeping us into an alternative universe, it lets us see the world we actually inhabit from another perspective.

Though Mr. Roth's premise opens the door to all kinds of apocalyptic scenarios, the Lindbergh presidency he refracts through the eyes of the young "Philip" and his Newark compatriots is not some B-movie horror tale with concentration camps springing up in Nebraska. He isn't writing a roman ý clef comparing anyone to Hitler, Lindbergh included, or saying that America is fertile ground for a Third Reich. That would be wasted breath anyway; Hitler, Goebbels and Leni Riefenstahl have lately been invoked so much by the left and right, even in tacky campaign commercials, that they're becoming as weightless as the Three Stooges. What Mr. Roth has drawn instead is far less horrific but all the scarier for being plausible rather than over the top. The book's low, at times mock-journalistic tone is antithetical to the election year hysteria of Bush haters and Bush boosters alike. The fear it unfurls is a cool fear, not that of an incipient holocaust.

Thus Mr. Roth's Lindbergh, a plain-spoken man of few words, never snarls, goosesteps or drapes himself in Nazi regalia. He is "normalcy raised to heroic proportions, a decent man with an honest face and an undistinguished voice who had resoundingly demonstrated to the entire planet the courage to take charge and the fortitude to shape history." He is for "entrepreneurial individualism" and against governmental tyranny. He is against the persecution of Jews. He reassures Americans that every decision he makes in the White House, including his willingness to blow off former allies opposed to his go-it-alone foreign policy, is "designed solely to increase their security and guarantee their well-being." And while there are a few pogroms along the way, their scattered fatalities and bottom-up provenance have more in common with the urban race riots of the late 1960's than with the programmatic state genocide of a totalitarian regime.

This America is still a democracy. But it is one in which a president can use fear, extra-Constitutional government surveillance and stagecraft (Lindy is constantly barnstorming the country in his plane, "Mission Accomplished" style) to impose a dangerous idÈe fixe. Meanwhile, his surrogates, including the voluble vice president, Burton K. Wheeler, question the patriotism of anyone who doesn't get with the program. That Mr. Roth can portray this America with a certain amount of wit and even vaudeville - the gossip columnist Walter Winchell ("America's best known Jew after Albert Einstein") becomes Lindbergh's most forceful nemesis - distinguishes this writer's voice from so much of the hectoring in our culture now. When everyone else in the room is shouting, Mr. Roth's piquant storytelling is what makes you want to listen and suspend disbelief.

Rather then erect a Dachau, the Lindbergh administration hatches a seemingly gentle plan to prod assimilation, not extermination. It's innocuously called Just Folks - a name that is itself almost a joke and is as benign-sounding as, say, "faith-based initiative." It's "a volunteer work program for city youth in the traditional ways of heartland life" and is administered by an Office of American Absorption fronted by an obliging and pompous rabbi of radio celebrity. The teenage Roth character who enlists in Just Folks is shipped off to a Kentucky tobacco farm, where his Christian host, like many of the non-Jews in "The Plot Against America," is nothing but lovely.

But what about those who choose not to participate in this program supposedly intended "to raze those barriers of ignorance that continue to separate Christian from Jew and Jew from Christian"? If you abstain, you are not Just Folks. You are not the Heartland. You are not, in the formulation of our current president, the "heart and soul" of your country. You are, perhaps, something less than an American.

Set against this backdrop is the real heart and soul of "The Plot Against America" - the Roth family and their Newark neighbors. Meet and judge them for yourself. But as this novel enters the culture, and some hell breaks loose in that way that Mr. Roth is a master of fomenting, it's worth taking the temperature of the country into which it is being sent. As there's no Nazi putsch in the book's counter-history, there is none on the horizon in America now. In that sense, the swastika on the cover of "The Plot Against America" is a red herring. But there are other ways for things to go wrong in America - as they did in the 1930's and as they did in the McCarthy and Vietnam eras apotheosized in other Roth novels.

In truth, we've only just begun to be tested. We are still in the very early stages of two wars whose ends are nowhere in sight. The war in Iraq has already been pinned on Jewish neoconservatives by Senator Fritz Hollings of South Carolina, a Kerry-supporting Democrat, as well as by right-wingers like the unrepentant Pat Buchanan, as if the non-Jewish president and vice president were not among its architects. The other war, which politicians of all stripes want to pretend is a war on a tactic (terrorism) and not about religion, is, as everyone else seems to know, being fought against a bastardized form of Islam. Not unlike Jews in the 1930's, the innocent American practitioners of that creed are alien to many in the heartland of just folks.

But in victory there are no scapegoats, and the president tells us daily that "we're making good progress.'' Freedom is on the march in Iraq, he says, and all the grave projections in our own intelligence reports are merely defeatist naysaying. Every presidential decision is made solely to increase our security. Our policy of pre-emptive war is F.D.R. incarnate, we're told, the very antithesis of Lindbergh isolationism.

As long as there's no explosive evidence to rain on that parade, Mr. Roth is entirely right to say that "The Plot Against America" cannot be squared with "the present moment in America." But what makes this book terrifying in its sly, even insidious way is that you can't read it without imagining how the combustible elements of our own home front might ignite if the present moment does not hold.