The previously unpublished work was written while Tolkien was professor of Anglo-Saxon at Oxford University during the 1920s and ’30s, before he wrote The Hobbit and The Lord of the Rings. The publication will make available for the first time Tolkien’s extensive retelling in English narrative verse of the epic Norse tales of Sigurd the Völsung and the Fall of the Niflungs.And from David Brawn, of HarperCollins UK —
It is an entirely unpublished work, dates from around the early 1930s, and will be published – all being well – in May this year. Otherwise the clue as to what the book will contain is in the title – THE LEGEND OF SIGURD AND GUDRUN. You will surmise from this that it is not a Middle-earth book, but we are confident that Tolkien fans will be fascinated by it.
Certainly something to look forward to! At least for the medievalists among us; pace Brawn, I would think the work will have only the most limited appeal to mainstream fans of Tolkien’s fiction. For those unfamiliar with the story of Sigurd and Gudrún, follow the link above for a summary of the Norse subject matter The Legend of Sigurd and Gudrún is expected to treat.
I suspect this work must be the “long unpublished poem entitled ‘Volsungakviða En Nyja’, probably written in the late 1920s or early 1930s. Tolkien described it, in a letter to [W.H.] Auden dated 29 January 1968, as ‘written in fornyrðislag 8-line stanzas in English: an attempt to organize the Edda material dealing with Sigurd and Gunnar’” . Coincidentally, I was just discussing this poem with someone no more than a week ago. The title is Old Norse and may be translated, more or less, as “The New Lay of the Volsungs”. How good is it, this poem? No way to know that yet, of course, but Tolkien described it as “a thing I did many years ago when trying to learn the art of writing alliterative poetry” . No doubt some will accuse Tolkien’s publisher, HarperCollins UK, of scraping the bottom of the barrel here, but even Tolkien’s “practice works” (perhaps even especially his “practice works”) hold great interest to scholars.
What is also unclear is the precise meaning of “long unpublished” in the note above — is it “long, unpublished” (i.e., the poem is long and has not yet been published), or is it “long-unpublished” (i.e., no comment on the length of the work, but rather on the duration of its languishment). Tom Shippey has pointed out that there is an 8-page gap in the Codex Regius manuscript of the Poetic Edda, specifically in the Sigurðr cycle ; if Tolkien’s poem was meant to fill that gap, as Shippey supposes, then we have reason to think it must be fairly short. If it is, then I hope the publisher doesn’t go overboard puffing it up into something “book-length” in the interests of profit. That may be a futile hope, but we will be very happy to have it, whatever its form.
UPDATE — On the other hand, if we’ve identified the right poem, and if its companion is also published with it (as seems likely), then we may have a pretty substantial publication after all. As Ardamir pointed out in the comments (below), the two poems are 339 and 166 stanzas, respectively, each of eight lines, for a total of more than 4,000 lines. Based on the number of lines per page in The Lays of Beleriand, this would translate into something on the order of 115 printed pages. Even with an introduction and other front matter by Christopher Tolkien, that’s still a fairly short book, but not as short as I feared. Nor is it likely to be a simple gap-filler for the eight lost pages in the Codex Regius. Perhaps Tolkien began with this in mind, but in his usual way, eventually embellished it far beyond its original ambit. And so, mirabile dictu, we have a new book by Tolkien — a mere seventy or eighty years later. :)
 Tolkien, J.R.R. Letters of J.R.R. Tolkien. Boston: Houghton Mifflin, 1981, p. 452 [note 3 for Letter #295].
 Ibid., p. 379.
 Shippey, Tom. “Tolkien and Iceland: The Philology of Envy.” Roots and Branches: Selected Papers on Tolkien. Walking Tree Publishers, 2007 , p. 192.