THE GOOD LORD BIRD. By James McBride. Riverhead Books. 417 pages. 27.95.

Mark Twain, that icon of Americana, would be nodding sagely. That's how good this National Book Award piece of fiction is. It's almost not fair that author James McBride is also an accomplished saxophone player and jazz composer.

"The Good Lord Bird" opens, "I was born a colored man and don't you forget it. But I lived as a colored woman for seventeen years." It haunts like that all the way through.

The narrator, Henry Shackleford, is a pre-pubescent slave in Kansas Territory in antebellum days. He runs away from his abusive master disguised as a girl, hoping the ruse can get him to the Underground Railroad instead of stolen and sold down the river.

And this isn't even his story. The young "girl" is taken up by the notorious abolitionist John Brown during Brown's bloody rampage through the territory. This is Brown's story, and the nation's story, seen through a fearful set of eyes unlike any other.

"(Brown's) face had so many lines and wrinkles running between his mouth and eyes that if you bundled 'em up, you could make 'em a canal. His coat, vest, pants and string tie looked like mice had chewed on every corner of 'em."

The abolitionist takes a shine to "Little Onion," whom he sees as a sign from God of his righteous crusade, much like the Good Lord Bird, the now extinct ivory-billed woodpecker whose feathers Brown collects and passes out as charms. Through one misadventure and another, Little Onion is forced to continue "her" charade as Shackleford follows Brown all the way to his monumental Harper's Ferry Raid and hanging execution.

Shackleford wavers between outright horror and rapt admiration, between a Judas-like betrayal and atonement. There is, in other words, enough allegory in this tale to flesh out a doctoral thesis, but you get too lost in the humor and humanity to mind. Just part of the fun is who among a large cast of gargoylic supporting characters does or doesn't realize Little Onion is a young man.

The evolution of the main characters rings like Freedom itself. Here's Shackleford, dressed for the first time as a man, visiting Brown in jail before the hanging: "The old face, crinkled and dented with canals running every which way, pushed and shoved up against itself for a while, till a big old smile busted out from beneath 'em all, and his gray eyes fairly glowed. It was like looking at the face of God."

As Twain once said, "Books are the liberated spirits of men."

Tell me about it.

Reviewer Bo Petersen is a reporter at The Post and Courier.