At the game of imagining strangers’ lives, Curtis Sittenfeld excels. It’s easy to envision her seated on a park bench or in a café, people-watching and making up stories to fit the faces in the crowd. Key questions in the game when the strangers are a couple: Why is she with him? Why is he with her?

As a nation of voyeurs for whom the salaciously personal frequently eclipses the political, we ask ourselves those same questions about the people we elect to office — most frequently after a sex scandal, when political couples are at their most humiliatedly human. But we ask them, too, when an evidently happy couple seems like a mismatch, when we can’t quite wrap our minds around how it was that, say, the bookish girl fell in love with the party boy. This is the question Ms. Sittenfeld (“Prep,” “The Man of My Dreams”) takes on with enormous sympathy in “American Wife” (Random House, 558 pages, $26), her widely anticipated and vastly entertaining roman à clef about Laura Bush, the most publicity-shy and therefore most enticingly enigmatic first lady in living memory.

On an almost blank slate, nearly anything can be written. All fears to the contrary, however, “American Wife” is no hatchet job, no gossipy Kitty Kelley bio in disguise. Nor is it hagiography or the sort of seamy political pulp fiction in which denizens of the Capitol have been known to dabble. Rather, it is an intelligent, well-crafted, psychologically astute novel that, granted, will anger the overly literal and the easily outraged. But such people are unlikely to be eager readers of contemporary fiction. This book is for those of us who are.

Ms. Sittenfeld’s Laura Bush stand-in is the thoroughly decent, entirely likable Alice Lindgren, an only child from tiny Riley, Wis. Growing up there, her most powerful influence is her Tolstoy-reading, cigarette-smoking, fashion-loving grandmother, though the quiet devotion and aversion to conflict that mark her parents’ marriage will come to shape hers as well.

Alice is a good girl who, at 17, is involved in a life-changing tragedy that will surface in her subconscious for decades afterward: She is at fault in a car accident that scarcely injures her but kills the boy she has a crush on. Already cautious, she becomes more so, though not before a trauma-induced period of surreptitious and extreme recklessness.

After high school, Alice goes away to college — not far, only to the state capital, Madison — and becomes first an elementary school teacher and then, because she reasons it will be like having reading period last forever, a school librarian. Passionate about books, passionate about children, she is enraptured by her work, dreaming up new things for the students on weekends, on summer vacation. One of her literary touchstones, then and always, is the children’s book “The Giving Tree,” Shel Silverstein’s parable of an affectionate but selfish boy and the tree who loves him enough to give all of herself to him, right down to the stump, in order to make him happy. For Alice, it is a guiding force. Ms. Sittenfeld, wisely, never explains its plot.

Alice is 31, pretty, and in a romantic dry spell when, at a backyard barbecue in Madison in 1977, she meets Charlie Blackwell, the wealthy, Princeton-educated son of the state’s former governor and the kind of loose, fun-loving ne’er-do-well who adds spark to a gathering just by joining it. He is handsome yet off-puttingly self-assured, and Alice is underwhelmed, but he is swiftly enchanted with her, and she soon recognizes the fundamental sweetness beneath his charm. Ms. Sittenfeld makes their rapid courtship — engaged after six weeks, married six weeks after that — seem both inevitable and right, not least because of their powerful physical attraction. Though it is necessarily more complicated, their enduring love makes at least as much sense.

When they meet, Charlie is on the verge of launching his first campaign, a doomed-to-fail effort to unseat a popular congressman in a district where Charlie doesn’t live. His right-hand man is Hank Ucker, a brilliant and ruthless strategist who had been his father’s assistant. This is, of course, Karl Rove, relocated to Wisconsin under an assumed name. When Alice first encounters Hank, she has a copy of John Updike’s “Rabbit Redux” in her hand; he promptly gives away the ending. She never does like him.

The Blackwells, whose family business is beef, are a Milwaukee-based political clan, large, raucous, and given to prizing loyalty above all else. The patriarch, Harold, is a softhearted man with a sentimental streak, and a kind father-in-law to Alice. The matriarch is the imperious Priscilla, whose four sons call her Maj, short for “Her Majesty.” She isn’t so much formidable (Alice, though quiet, isn’t easily cowed) as she is overtly vicious. Barbara Bush’s talons-bared characterization of Geraldine Ferraro, her husband’s counterpart on the 1984 Democratic ticket, comes to mind: “rhymes with ‘rich.'”

The backdrop of “American Wife,” a book that begins when Alice launches into the story of her life after a particularly fraught day as first lady in June 2007, is political by default. But the vast majority of it is about Alice’s life before Charlie and the first decade or so of their life together: their young marriage; their only child, Ella (who is neither a Bush twin doppelgänger nor a Jenna-Barbara composite); Charlie’s drinking, which nearly destroys them. It is Alice’s story, not Charlie’s or the Blackwell family’s, and, fittingly for such a private protagonist, the essence of the book is personal. Its most lovable, most vivid secondary characters are Alice’s intimates, the women closest to her: her staunch and effervescent grandmother, Emilie; her ebullient sister-in-law and friend, Jadey; her chief of staff at the White House, whose identity it would be a terrible spoiler to disclose.

In the book’s final section, Alice’s past rears up to haunt her and to help her, reminding her of who she once was, and she does at last make a political statement that feels, suddenly, necessary to her. But in any number of ways, Alice is agnostic. She doesn’t share her husband’s religious faith, let alone his born-again fervor, and she tends to believe that running the government, like taking public political stands, should be left to those whose job it is to do so. She is a good political wife; generally, unless it’s helpful to her husband, she doesn’t give her opinion on controversial topics. And she is, like so many readers, more an observer than a person of action.

Ultimately, it is a novelist’s argument that Ms. Sittenfeld makes: that anyone who reads as many novels as Alice does must see human beings and human relationships as endlessly complex, must understand that situations are almost never black or white, must be able to put herself in the shoes of another and imagine what that life feels like. That is not the way this red state-blue state nation frames things, but it might be the element of fiction that is most true.