It's difficult to write a book on a figure like Joan of Arc. First, there's the competing claims about her claims. Do we interpret her through a religious lens that accepts the possibility of the supernatural. Do we approach it from an Enlightenment perspective, where a demythologization is the goal. A hagiography or a de-personalizing often are the results.
Harrison navigates the task as well as I've read. She provides a significant look into the life and the overall background of Joan of Arc, including the cultural and religious issues, and how the narrative has been used in the midst of broader political contexts.
She does not commit to a purely religious perspective, but she understands it well and she seeks to portray as accurate a picture of Joan as possible in light of today's knowledge and interpretive tools.
Very high quality research, very well written, great balance of narrative and interpretation. A model for historical biography.