A "new" book by J.R.R. Tolkien goes on sale on Tuesday which may well be the author's last complete work to be published posthumously, according to Reuters.

Tolkien's son and literary executor Christopher, now in his eighties, constructed "The Children of Hurin" from his father's manuscripts, and said he tried to do so "without any editorial invention".

Already told in fragmentary form in "The Silmarillion", which appeared in 1977, the new book is darker than The Hobbit and "The Lord of the Rings", for which Tolkien is best known.

The story is set long before "The Lord of the Rings" in a part of Middle-earth that was drowned before Hobbits ever appeared, and tells the tragic tale of Turin and his sister Nienor who are cursed by Morgoth, the first Dark Lord.

David Brawn, director at Tolkien publisher HarperCollins, said the initial worldwide print run for the new book, featuring illustrations by Oscar-winner Alan Lee, was 500,000.

Hollywood studios are eager to buy the film rights of the new book, according to Brawn. "We all want this first and foremost to enjoy life as a book," and went on to say "No one's saying never to a film (but) the film rights are reserved by the estate. We want to see what reaction it gets and then let it run its course."