“Every man that writes is writing a new Bible, or a new Apocrypha; to last for a week or a thousand years,” the Scottish philosopher Thomas Carlyle recorded in his journal in 1832. Hyperbole, maybe, but on the other side of the Atlantic it seemed nearly true. Early nineteenth-century America was a time and place peculiarly receptive to new prophets and their books. Two lively cultural currents combined to make it so. One was the drive, in the heady early decades of the Republic, to create a uniquely American literature. The other was a national religious mania known as the Second Great Awakening, whose epicenter was western and central New York State. Between the Revolutionary and Civil Wars, countless revivals and new religions flared up from the Finger Lakes to Niagara Falls.

Many of the newer sects flamed out. The Shakers’ demise was no surprise, given their celibacy. The Oneida Community taught free love but lives on today only as a silverware company. Others persisted in new forms. The Millerites believed that Christ would reappear on October 22, 1844; their faith was severely challenged when that day passed without incident, though a version of Millerism survives with the Seventh Day Adventists. The most impressive and unlikely survivor from New York’s religious bumper crop is the Church of Jesus Christ of Latter-day Saints. A hundred and fifty million copies of its central scripture have been printed since its first edition, in 1830. The Book of Mormon is where the literary and spiritual ambitions of the antebellum age most tenaciously converged.

And yet the Book of Mormon has excited very little enthusiasm outside of Mormonism. The typical reaction among the few non-Mormons who’ve read it is to deride it. (Mark Twain called The Book of Mormon “chloroform in print.”) One exception is Avi Steinberg, a self-described “fascinated nonbeliever,” who has spun his curiosity into a playful book titled “The Lost Book of Mormon.” Steinberg nominates the Mormon scripture as a Great American Novel, or, failing that, as a priceless artifact from the Old, Weird America—a uniquely American product, like jazz music and superhero comics, that deserves our attention.

From the Vedas to “Dianetics,” scripture is a literary category that defies genre. The body of texts variously held up as “scripture” include prophecies, biographies, letters, poems, songs, parables, laws, histories, dream diaries, genealogical lists, memoirs, and epics. Like the New Testament, the Book of Mormon is presented as a divinely inspired anthology, the mostly chronological record of a people from about 600 B.C. to about 400 A.D. (with one digression to a more ancient period). But the story of its compilation differs markedly from that of the New Testament: The religion’s founder, Joseph Smith, claimed that his source for the book was a set of gold plates that he’d excavated from a hillside; he credited himself as the text's mere translator. And, according to a story told by Smith’s successor, Brigham Young, Smith was once permitted a glimpse into a secret cavern on that same hillside, which was chock full of further scriptures that weren’t ready to be revealed, “more plates than many wagon loads ... piled up in the corners and along the walls.” The scholar Laurie F. Maffly-Kipp, in her introduction to the Penguin Classics edition of the Book of Mormon, writes that the book’s very existence “implied (and the narrative itself stated) that there were many records still to be discerned. God was once again speaking to his people, and the canon of scripture had therefore been reopened.”

As for Steinberg, the genre he’s chosen for “The Lost Book of Mormon” is mostly travelogue. His first stop is Jerusalem, where he struggles to find a local copy of the Book of Mormon. (It has received official translations into scores of languages, but Hebrew is not among them.) Jerusalem is where the Book of Mormon begins, and it starts with a murder: One desperate night near the city walls, the Mormon prophet Nephi, a contemporary of the Old Testament’s Jeremiah, must kill his wicked relative Laban in order to recover a precious family book written on plates of brass. Steinberg is struck, as many have been before him, by just how small the Holy Land is. “The great kings of the Bible were in fact small-time clan leaders; the grand battles more closely resembled shepherd’s squabbles,” he writes. Most scriptural characters show up only passingly in secular history. (The non-Biblical prophets in the Book of Mormon don’t appear in historical records at all.) The prophets’ visions transform backwaters into grand landscapes—perhaps precisely because the places they’re from are small. “The lavishness of a biblical imagination,” Steinberg writes, “is sometimes born out of a poverty of space and resources, from a poor person’s urgent need to amplify.”

Steinberg rarely quotes directly from the Book of Mormon, which seemed odd until I tried to read it myself. As exciting as the plot sounds in paraphrase, the actual text smothers it in so many King Jamesian locutions that it’s barely discernable. No one’s ever claimed that the Book of Mormon rivals the literary achievements of the Bible or the poetic grace of the Koran in Arabic, but I was still surprised by the tedium. Of course, scriptures are often a hard slog for non-believers. Their unsettled position between fiction and nonfiction leaves the secular reader wondering: How am I supposed to take this stuff? As myth? Metaphor? Historical novel? Hallucination? Even the religious sometimes give the actual reading of scripture a pass. (I know a former Catholic seminarian who admitted that he’s never read the Bible in its entirety.)

In the case of the Book of Mormon, only in 1986 did a prophet, Ezra Taft Benson, order that Mormons study the book closely. “The drama of authorship, of the book’s discovery and its translation,” Steinberg writes, “was for many years the story, the thing that bewitched readers, the thing that made people’s blood boil.” The fact of its existence—an original American scripture—mattered more to its early audience than the narrative it contained. As it happens, that narrative takes place largely in Mesoamerica, and for some current-day Mormons, Mayan ruins have become a place of pilgrimage. Many centuries before Columbus, the Book of Mormon tells us, ocean-faring Hebrews set sail from Jerusalem and landed in Mesoamerica. In “The Lost Book of Mormon,” Steinberg tags along with a tour group to Guatemala and southern Mexico—or, as the Book calls them, the Lands of Nephi and Zarahemla.

A visit to the National Museum of Guatemala offers a fascinating glimpse of Mormon exegesis at work in the field. In one gallery, on a Mayan altar adorned with symbols, a tour guide points out a glyph that could be interpreted as meaning “and it came to pass.” To the pilgrims, this is hugely significant, because “and it came to pass” is the most famous recurring phrase in the Book of Mormon, with a thousand three hundred and eighty-one appearances. Few paragraphs begin without it. To Mormon detractors, Steinberg notes, it’s a telling verbal tic that strongly suggests “a weak ventriloquism of biblical idiom.” For believers, the incessant repetition of the phrase is “like a charming quirk of one’s beloved.” And, more than that, it’s a sign—it must be, given that it appears in scripture. To readers of faith, Steinberg writes, “everything, every mystery, every slightly odd detail, would eventually reveal something.”