Karen Russell’s 2006 collection of short stories, St Lucy’s Home for Girls Raised by Wolves, was as notable for its odd, often fantastic, take on growing up as it was for its memorable title. Last year, Russell, now 29, appeared on The New Yorker’s “20 Under 40" list of promising young writers who the magazine believed would be significant in the years to come. Swamplandia!, her first novel, recently achieved a place on this year’s Orange Prize longlist.

Swamplandia! is an extension of Ava Wrestles the Alligator, one of the stories in St Lucy’s Home. As in many of her short stories, Russell adopts the voice of the adolescent. The narrator of most of Swamplandia! is a teenaged girl, Ava Bigtree. Ava is the daughter of Hilola Bigtree, the famous alligator wrestler.

Swamplandia! Chatto and Windus, 316 pages, £12.99 (around 940).

Matters are worsened by the advent of a big, hell-themed amusement park not far away. Ava and her sister Ossie are left alone on the resort. Ossie falls in love with a ghost and first she, then Ava, must embark upon a journey to the Underworld. Meanwhile, their brother Kiwi must deal with an underworld of his own; life on the mainland at the World of Darkness theme park.

Once Kiwi leaves Swamplandia! the book is divided in two—the chapters that follow Kiwi are alternated with Ava’s point of view. Kiwi’s journey parallels Ava’s own, yet the contrast between the two worlds is always clear. Where Ava must dive into the water with the alligators to prove herself, Kiwi must rescue a swimmer from a pool where the water is dyed red.

Russell emphasizes the contrast with her prose; the utilitarian language of Kiwi’s sections of the book could not be more different from the startling, lush account of Ava’s journey through the swamp. “Stands of pond-apple trees were adorned with long nets of golden moss and shadowed a kind of briary sapling I didn’t recognize. Air plants hung like hairy stars. We poled through forests. Twinkling lakes. Estuaries, where freshwater and salt water mixed and you could sometimes spot small dolphins. A rotten-egg smell rose off the pools of water that collected beneath the mangroves’ stilted roots."

The division of the book into “Ava" and “Kiwi" sections has its drawbacks. The contrast between the sterile World of Darkness and the Everglades may make sense, but compared with the over-the-top loveliness of Ava’s sections, the ones focusing on Kiwi fall rather flat. The middle child, Osceola, never gets a voice and is never a fully realized part of the story. In the central sections of the book, where Ossie’s relationship with the ghost develops, the pace slackens considerably. A long chapter giving the ghost a background story feels rather orphaned in the middle of the text, though it is a fine piece of writing in its own right.

Russell makes the question of whether this is fantasy or magical realism (or simply the characters’ own imagination) irrelevant. The writing shifts easily between the mythic and the real. Ava is in many ways still a child, and her age allows for this constant moving between registers. On at least one occasion this shift leads to a devastating revelation. The fantasy elements of the story are intangible and unsettling, but fit perfectly.

For all its strangeness, Swamplandia! is also the account of a family’s coming of age after a huge loss. As a family drama it is funny, moving and honest. “‘I’m not going anywhere,’ she told me that night. But until we are old ladies—a cypress age, a Sawtooth age—I will continue to link arms with her, in public, in private, in a panic of love."

Russell never quite manages to keep up the brilliance that displays itself in long stretches of this first novel. But these heights, when they are reached, are extraordinary. While Swamplandia! is far from being a perfect book, it is the sort of book that makes you glad that the author is still at the beginning of her career.

Write to lounge@livemint.com