'The Story of Kullervo' was written when Tolkien was at Oxford in 1914 as a 22-year-old, though it was never completed. It was his first piece of prose fiction.
It tells the story of a doomed young man who is sold into slavery and swears revenge on the magician who had killed his father.
Tolkien alighted on the subject matter when he was studying Finnish grammar -- he was a philologist -- and was intrigued by the character Kullervo, a vengeful and misguided youth, from The Kalevala, a 19th-century Finnish epic, The Sunday Times reported.
John Garth, a Tolkien biographer, was quoted as saying, "It's a very important and significant book, but more for being vital in Tolkien's development as a writer. Most crucially, it led to his Elvish languages for Middle-earth. So this book is key to him inventing languages of his own for later works. But, interestingly, he deliberately never completed it. He just knew he could write, but wanted to move on."
Tolkien, whose The Hobbit and Lord of the Rings books have become popular film series, admitted in letters, published in the early 1980s, that 'The Story of Kullervo' was "the germ of my attempt to write legends of my own."
The Story of Kullervo, which is only a few thousand words long, will be brought out in August by HarperCollins, the publisher of his novels. The cover features one of Tolkien's own illustrations.
Over the past decade, a handful of Tolkien's previously unpublished works, such as The Children of Hurin, The Legend of Sigurd and Gudrun, and the poem The Fall of Arthur, have been released.