Tolkien on Fairy-stories is a new publication co-authored by Verlyn Flieger and Douglas A. Anderson that contains the entirety of J.R.R. Tolkien's essay On Fairy-stories. This is a new expanded edition of Tolkien's most famous, and most important essay, which defined his conception of fantasy as a literary form, and led to the writing of The Lord of the Rings. The first version of this essay was published in Tree and Leaf (1964); however, this is a new expanded version comprising of 18,000 words and also contains many more pages of his views that were originally condensed into or cut from the published proper version. An estimate is difficult, but these unpublished passages perhaps amount to half again as much writing as the essay itself (Harper Collins **) . Currently, there is only publishing information from Harper Collins on the UK Amazon site. The tentative release date is set for October 1st, 2007. You can read more here.