A previously unpublished short story by J.R.R. Tolkien will release in the U.K. next week, and it promises to give a fascinating look into one of the literary giant's first experimentations with fantasy writing.

"The Story of Kullervo" is Tolkien's retelling of "The Kalevala," the dark 19th-century Finnish epic about an orphan who avenges the massacre of his family and accidentally seduces his own sister before taking his own life.

"Tolkien did say that he wanted to do his own thing with ("The Kalevala"), so I'd be intrigued to see what his Christian imagination does with that pagan story," said Joseph Pearce, a Tolkien expert and director of the Center for Faith and Culture at Aquinas College in Nashville.

Though "The Story of Kullervo" went unfinished and unpublished, Tolkien considered it "the germ of my attempt to write legends of my own", according to The Guardian. The unfinished manuscript was the foundation for Tolkien's later work The Silmarillion.

Tolkien began writing "The Story of Kullervo" at age 23, when he was an English student at Oxford University. He and C.S. Lewis had a shared love for Norse mythology at the time, and Pearce said that is likely how Tolkien first discovered "The Kalevala."

"They loved the storytelling, the fantasy of the whole thing," Pearce explained. "But also, there is a sense in which man, if he believes himself to be master of his own fate, he's actually mastered by his fate. In other words, that we're not gods and when we try to make ourselves gods, we are headed for destruction."

"That's something that unites the paganism of the Norse myth-makers and the Christianity of Tolkien and Lewis."

The murderous revenge, incest, and suicide found in "The Story of Kullervo" do not seem to be typical themes of Christian literature. However, Tolkien was not the only Christian author to explore darker themes in the early 20th century: G.K. Chesterton's "The Man Who Was Thursday" published in 1908 and T.S. Eliot published "The Wasteland" in 1922.

Pearce explained the Christian fascination with darkness saying, "the modern world is very dark and if depicted in its ugliness, it's made to be truthful."

The moral truth behind "The Story of Kullervo"? Pride goeth before a fall.

"When we believe we're master of our own fate, we're actually heading for a fall," Pearce said.

"The Story of Kullervo" will publish August 27 in the U.K., and April 2016 in the U.S. In the meantime, Tolkien enthusiasts can check out another of his early works, The Children of Hurin, which published posthumously in 2007.