This was sent to one of the Tolkien lists I'm on.
TheOneRing.net has posted Christopher Tolkien's prologue to the book Sigurd and Gudrun, written by J.R.R. Tolkien in the 1930's, due out on May 5th. I've got to say it explains more about the work and what it is. The link is: http://www.theonering.net/torwp/2009/04/22/31886-christopher-tolkiens-foreward-to-sigurd-and-gudrun/