Brady Udall has a thing for great opening lines. His debut novel, 2001's The Miracle Life of Edgar Mint, began with one of the greatest first sentences of all time: "If I could tell you only one thing about my life, it would be this: When I was seven years old, the mailman ran over my head." The Lonely Polygamist, his sophomore novel published last month, has an intriguing first line—"To put it as simply as possible: This is the story of a polygamist who has an affair"—but it doesn't get really good until the second sentence: "But there is much more to it than that, of course; the life of any polygamist, even when not complicated by lies and secrets and infidelity, is anything but simple."

You can tell a lot about Udall's two novels from those openings: Edgar Mint was a kindhearted comic novel, peppered throughout with surprising bursts of humor. While Polygamist definitely has its humor—a quarter of the book is told from the perspective of a mischievous 11-year-old boy with a penchant for explosives who suffers from chronic foot odor—it's much more invested in explaining and understanding the complexities of the life of Golden Richards, a small-­business owner and Mormon with four wives and 28 children. Richards, a large, awkward, shy man, is part of a semi­secret Ohio polygamist sect in the 1970s, and, thanks to Jimmy Carter's malaise economy, his construction business has hit the skids, forcing him to take a job building an addition to a Nevada whorehouse. (Richards makes his employees promise to not visit the brothel, a demand that begins to diminish morale after a few weeks of hard labor in the desert.) So far away from his family, Richards meets and embarks on an affair with a strange woman, cheating on four wives at the same time. His is not the only affair in the book.

Polygamist explores the problems of multiple marriage:

Sex was one thing she and the other wives never spoke of, and though she knew there was very little in the way of advanced lovemaking going on with them or with other members of the church (the unspoken law was that sex was meant for procreation and nothing but), she couldn't help but wonder.

and

One of the children, Daughter #11, has started a rumor that has been picking up steam among the under-seven segment of the domestic population, that Mother #3 is disappearing, fading in and out, flickering into nothing at inopportune and often comical moments, like a ghost in a black-and-white cartoon.

In a polygamous relationship, people get forgotten. People get jealous. People feel left out. The emotions are no different, in other words, than in the "traditional" American nuclear family. Udall uses this macrocosm of a family to explore the nuclear unit upon which America is supposedly based (it's not a coincidence that Polygamist is full of nuclear explosions; when Richards was little, his father used to get him up before dawn and take him to the desert, where they'd watch mushroom clouds blossom on the horizon).

In many ways, Polygamist is interesting for what it doesn't explore: For instance, Udall—part of a large, prominent Southwestern Mormon family and a graduate of Brigham Young University—barely mentions Mormonism in the book. The Book of Mormon makes a few token appearances, a cameo character skirting the edges of the action, like a visitor from another novel on a nearby shelf, but this isn't a religious satire. Udall makes no judgment about Richards's family, and moral lessons—remember, kids: Polygamy is baaaaaaaad—are nowhere to be found. Like most members of families, Richards isn't portrayed as a man with much of a choice; he just has to make the best of what he has.

It's overly diminishing to refer to Polygamist as just a novel about families. This is the kind of thick, wildly entertaining book that seems to be about everything at once. Critics seem to be legally required to use the words "Great American Novel" when writing about Polygamist, and I am forced to agree: This is a Great American Novel in much the same spirit as Middlesex or The Brief Wondrous Life of Oscar Wao, wide-ranging in scope and enlightening in its specificity about a subculture that feels previously unexplored in literature. A subplot involving a wad of gum caught in his pubic hair serves as both comic relief and a symbol of Richards's sexual fears. A cuckolded Nevada businessman simultaneously grows and shrinks in stature and fearsomeness as the villain of the piece and a victim of embarrassment. An ostrich named Raymond appears like a grim reaper in times of great peril. The last lines of Polygamist—I'm not going to share them here; it has to be earned to be truly enjoyed—are just as crisp and altogether perfect as the first. It hums all the way through, with virtually no missteps; it's the Platonic ideal of a summer book—a novel in which you can get lost and find yourself at the same time. recommended