I just finished reading this.  I had read Unflinching long ago, Edgar's actual diary found in the cabin stove.  Cold Burial fills in a lot of gaps in what led to the "adventure" and some bio on the adventurers.
Currently Unflinching is hard to find and expensive if you find a copy.  Another book about the same thing is Death in the Barren Lands, which I also have not found but I suppose on occasion one could locate a copy or at a bigger library???