This omnibus of Gird's life and legacy adds useful historical background to the Paksenarrion and subsequent books. So must be read for maximum understanding of the issues raised during those books. But the writing isn't good enough or the subject compelling enough to make it a book to read for itself.
I read it before reading Crown of Renewal as recommended by the author. There are a few consistency issues between the life of Gird and what is reported in the main-line books, explainable by inaccurate historical accounts of Gird. In that there are obvious parallels with real-world religions. There are also inconsistencies between the post-Gird portions of the book and later discoveries in the main-line books, in one case requiring a very contrived time-travel episode.
A couple of well-developed characters simply vanish into the mists of history. It would have been good to see their legacy, though that is probably discernible to those who've read the whole set.
So for Paksenarrion readers a four star, but maybe only two or three for new readers.