Readers who picked up The New York Times on March 13, 1852, might have seen a small advertisement on Page 3 for a serial tale set to begin the next day in a rival newspaper.

The story, which was never reviewed or reprinted, appears to have sunk like a stone.

But now comes another rich revelation: The anonymously published tale was nothing less than a complete novel by Walt Whitman.

The 36,000-word “Life and Adventures of Jack Engle,” which was discovered last summer by a graduate student, was being republished online today by The Walt Whitman Quarterly Review and in book form by the University of Iowa Press. A quasi-Dickensian tale of an orphan’s adventures, it features a villainous lawyer, virtuous Quakers, glad-handing politicians, a sultry Spanish dancer and more than a few unlikely plot twists and jarring narrative shifts.

“This is Whitman’s take on the city mystery novel, a popular genre of the day that pitted the ‘upper 10 thousand’ — what we would call the 1 percent — against the lower million,” said David S. Reynolds, a Whitman expert at the Graduate Center of the City University of New York.

But it also, Reynolds and other scholars who have seen it say, offers clues to another mystery: how a workaday journalist and mostly conventional poet transformed himself into the author of the sensuous, philosophical, wildly experimental and altogether unclassifiable free verse of “Leaves of Grass.”

That transformation was one that Whitman himself wished to obscure.

That doesn’t faze Zachary Turpin, the graduate student at the University of Houston who found “Jack Engle.”

Turpin called it “rollicking, interesting, beautiful, beautiful and bizarre,” with antic twists, goofy names and suddenly revealed conspiracies that recall “a pre-modern Thomas Pynchon” or even, he ventured, “It’s a Mad, Mad, Mad, Mad World.”

This may sound a long way from “Leaves of Grass.” But Jack Engle and the other raffish young male characters, Reynolds said, are reminiscent of the man-of-the-streets persona he created with “Leaves of Grass.”

And then there’s Chapter 19, which Ed Folsom, editor of The Walt Whitman Quarterly Review called “a magical moment.” Here, Jack enters the cemetery at Trinity Church in Lower Manhattan, and the madcap plot grinds to a halt in favor of reveries about nature, immortality and the oneness of being that strikingly echo the imagery of Whitman’s great work.