Even with his 26th book about to appear in bookstores, Philip Roth is still revising. Now 71, Roth has won just about every major American award a novelist can win, but a casual suggestion — that he has been insufficiently cruel to one of his characters — gets him pondering. "I didn't think of something like that happening to him," he says, musing aloud. "I guess — you know, it's interesting that you bring that up. It's too late for me to make any changes — the finished book just arrived today — but I wonder what I could have done ..."

That little speech should tell you three things about Roth. First, he never stops working. He's coming off a millennial hot streak that includes three astonishing books — Sabbath's Theater, American Pastoral and The Human Stain. For another writer, those would have constituted a distinguished career all by themselves. Second, he is constantly surprising — never forget (and perhaps he sometimes wishes we would) that this is the guy who wrote a novella about a man who literally turned into a gigantic breast. Third, Roth sees the world as a tangle of hypotheticals and what-ifs, of counterlives and forking paths and roads not taken. It is down one of those roads that his new novel lies. A chronic reviser, Roth is ready to rewrite history.

The Plot Against America (Houghton Mifflin; 391 pages) began in early spring 2001 with a single sentence, not one of Roth's own but a chance comment by the historian Arthur Schlesinger Jr., who speculates in his autobiography that in 1940 some right-wing members of the Republican Party considered drafting the pioneering pilot Charles Lindbergh as a presidential candidate. "That's it," Roth chuckles over the phone, surprisingly relaxed and wry for a man who jealously guards his privacy. "That's all it took. It should always be that easy!"

That single seed, rooted in Roth's singular imagination, grew into an entire alternative world. The Plot Against America is set in a shadow country that never was, an America in which Lindbergh, an isolationist in real life, defeated Franklin Delano Roosevelt to become the 33rd President of the United States of America. Armed with that premise, Roth takes readers on a harrowing safari across interdimensional borders into a bizarro version of his hometown, mid-century Newark, N.J., where we encounter Roth's own family and Roth himself as a child, living under the Lindbergh Administration. "My little rubric that I would recite to myself," Roth says, "was 'Don't invent it, remember it.'"

Decked out dashingly in jodhpurs and flight goggles, Lindbergh runs on a single plank: he will keep the U.S. out of World War II. And he's as good as his word. Once elected, he makes peace with Hitler at a conference in Iceland, fetes German diplomats at the White House and establishes the chillingly plausible Office of American Absorption, a government agency aimed at "encouraging America's religious and national minorities to become further incorporated into the larger society" — in other words, forcibly breaking up Jewish communities and dispersing their members to rural backwaters per the novel's Homestead Act of 1942. Roth's delivery is so matter-of-fact, so documentary deadpan that when we're 10 pages into the book our own world starts to seem like a flimsy fantasy.

Meanwhile, the national political drama is writ small in the subtle havoc it wreaks on Roth's family. This is one of the most personal books Roth has ever written. "People think I have, but I never really have written about my family on the nose before like this," he says. In The Plot Against America, the narrative is routed through the fictional Philip, 7, a hypersensitive, self-centered boy with a penchant, but not a talent, for running away from home. There's an aching warmth to Roth's rich portrait of the Jewish Newark of his youth, where the men play pinochle and the women mah-jongg, local punks go by names like Knuckles Kimmelman and Duke "Duke-it-out" Glick and everybody listens to Walter Winchell on Sunday nights.

But Lindbergh's presence in the White House puts pressure on Roth's family idyll, which promptly cracks. Philip lives in awe of his elder brother Sandy, but Sandy idolizes Lindbergh and thinks all the fuss over his repressive measures is hysterical Jewish paranoia, a view that drives their parents crazy. To make matters worse, Philip's aunt marries a collaborationist rabbi. As the noose tightens, Philip's father loses his job as an insurance salesman, and Philip's mother vibrates between stoic resistance, barely stifled panic and utter paralysis.

Most of this is fiction, but not all. "The legacy of the long chronicle of anti-Semitism was fear," Roth says. "I certainly felt it as a kid growing up in the late '30s and '40s." In fact, the ways in which politics impinges on domestic arrangements is the great subject of Roth's late period. Over the past decade, he has serially demolished households by means of McCarthyism (I Married a Communist), racism and political correctness (The Human Stain) and Vietnam (American Pastoral). "History comes into the house," Roth succinctly explains it. "I'm interested in that." It doesn't wipe its feet on the welcome mat either. Did Roth, while he wrote, ever wince at the ordeal he was putting his fictional family through? He did not. "I don't wince when I write," Roth jokes. "I wince in life."

It wouldn't be hard — in fact, it would be pretty easy — to read The Plot Against America as a political screed about contemporary America, lightly antiqued to look like a period piece. And it confuses matters further that Roth recently referred to President George W. Bush in the New York Times as "a man unfit to run a hardware store let alone a nation like this one." So is it an allegory or isn't it? "Well, it ain't," says Roth. "It's about an imagined America in 1940. Look, the immediate moment often colors reading — there's nothing wrong with that. But I don't think that's a lasting relevance that the book will have." Or, as Samuel Beckett put it, no symbols where none intended.

We live in America — the real America, thank God — so we're free to read however we want. But to read The Plot Against America as, say, a book about the reduction in civil liberties in the name of homeland security would be to drastically impoverish its rich complexity. In Roth's fiction, politics is an element that doesn't naturally occur in its unalloyed form. It's always getting confused and mixed up with shame and anger, baseball and sex. Philip's foxy aunt Evelyn is a stone-cold Lindberghite fascist, for example, but the little boy still gets a confusing, involuntary preadolescent hard-on when she hugs him. The Plot Against America is about how we experience history: dimly, through the dirty lens of our own trivial circumstances, and backward, without the benefit of hindsight. "The terror of the unforeseen," Roth writes, "is what the science of history hides, turning a disaster into an epic."

The Plot Against America is a sobering novel, but it's not a bleak one. As with an optical illusion, the longer you stare at Lindbergh's fascist U.S., the more clearly you see a shimmering vision of the real America, outlined in negative space, and you feel the tenderness with which Roth regards its fragile greatness. "I think this book is wholly optimistic," Roth says. "You know why? It never happened! At a time when it might have happened, it never happened. That's pretty terrific, you know?" At 71, Roth may just have written his first love letter.

• Lev Grossman