The first new Tolkien novel in 30 years will be published next month.
In a move eagerly awaited by millions of fans, The Children of Hurin will be released worldwide on April 17, 89 years after the author started the work and four years after the final cinematic instalment of the Lord of the Rings trilogy, one of the biggest box office successes in history.
The book, whose contents are being jealously guarded by publisher HarperCollins, is described as "an epic story of adventure, tragedy, fellowship and heroism".
It is likely to be a publishing sensation, particularly as it is illustrated by veteran Middle-earth artist Alan Lee, who won an Oscar for art direction on Peter Jackson's third film, The Return of The King.
Lee provided 25 pencil sketches and eight paintings for the first edition of the book.
Tolkien experts are already tipping The Children of Hurin - which features significant battle scenes and at least one big twist - for big-budget Hollywood treatment. Box-office takings from the Lord of the Rings trilogy to date are $4 billion or more.
Chris Crawshaw, chairman of the Tolkien Society, said: "It would probably make a very good movie, if anyone can secure the film rights.
"Tolkien saw his work as one long history of Middle-earth: from the beginning of creation to the end of the Third Age. The Children of Hurin is an early chapter in that bigger story."
Christopher Tolkien, using his late father's voluminous notes, has painstakingly completed the book, left unfinished by the author when he died in 1971.
The work has taken the best part of three decades, and will signify the first "new" Tolkien book since The Silmarillion was published posthumously in 1977.
"It will be interesting to see how it stands up today alongside all the Tolkien-like literature that we've become familiar with," said David Bradley, editor of SFX magazine.