A satanic figure slithers up onto the water tower of a mythical Mississippi town called Lake Belle Reve, takes in the family feud down below and utters a self-satisfied literary pronouncement that seems to sum up the dramatic intentions of this show’s famous authors.

“It’s Tennessee Williams in hell,” says this tattooed ring-meister character called the Shape. “I love it.”

It’s true. The Spanish moss fairly drips over “Ghost Brothers of Darkland County,” the new musical by Stephen King (book) and John Mellencamp (music and lyrics) that opened Wednesday night at the Alliance Theatre in Atlanta. These first-time musical theater writers are infatuated with the idea of the Southern Gothic.

There may be some gothic elements to the production itself. King and Mellencamp have been working on it for 12 years, having been paired by a mutual agent. The show was originally scheduled to premiere at the Alliance in 2009 but Mellencamp had disagreements with the director, so a new one, Susan V. Booth (who runs the Alliance), was brought aboard.

The story ricochets between 1967 and 2007. As a boy, central character Joe McCandless (Shuler Hensley) secretly witnessed his two brothers — and the girl they were fighting over — die. Forty years later, he fears his two warring sons may be headed for a similar fate. King's conceit is to have the ghosts of the past mingling with the real-time story. (And, in an instance of art imitating the life of its authors, one of the McCandless sons (Justin Guarini) wants to be a rock star, while the other (Lucas Kavner) has just sold his first novel for half a million dollars.)

The Shape (Jake La Botz) lives in a shadow world somewhere between a “True Blood” vampire king and the MC in “Cabaret.” The show's premise may be thin but he is slithering, salacious, manipulative, delightful.

Mellencamp digs deep into the soul of Southern roots music, offering up a score that references honky-tonk blues (“Tear This Cabin Down,” “Put Me in the Ground”) and tortured, Johnny Cash-style anthems of sorrow that suit Hensley’s monumental baritone (“What Kind of Man Am I”). Cash’s old bass player, Dave Roe, is in the band, which sits perched above the action in what looks like a slice of a House of Blues, and music director T Bone Burnett has nuanced the sound into a sleekly polished landscape.

Some of the most haunting moments of “Ghost Brothers,” which continues through May 13, come by virtue of the design. Thanks to Adam Larsen’s projections, a bloodbath worthy of “Hamlet” is distilled into streaks of red, which drip down a flickering scrim as the Shape struts off like some diabolic cowboy.

At Wednesday night’s curtain call, King, Mellencamp and Burnett all appeared onstage. Mellencamp’s girlfriend, Meg Ryan, and basketball commentator Charles Barkley were also in the house. Mellencamp looked ecstatic. He picked up director Booth and twirled her.

The Atlanta Journal-Constitution reviewer said the production lived up to the hype “with an almost supernatural ease.”