Grigsby received a Bachelor's degree in Prehistoric European Archeology and History and a Master's degree in Celtic Studies. He made contributions to (Graham Hancock)'s Heaven's Mirror and the television series based upon the book, Quest for the Lost Civilization. He is co-author of The Mars Mystery (with Graham Hancock and Robert Bauval). His book Warriors of the Wasteland (Watkins, 2002) examined the Medieval legends of the Grail in light of Indo-European, especially Celtic, myth. Beowulf and Grendel (Watkins, 2005) interprets Beowulf as "the recounting in poetic form of a religious conflict between two pagan cults in Denmark around AD 500" (p. 5).