Very interesting about Twain and Joan of Arc ... may have to get that biography.
I would highly recommend it to everyone, across the board, even those not interested in Catholic Saints or the Hundred Years War, as I consider it essential in so many areas of understanding.
Twain said it was by far the work of which he was most proud. He spent 10-15 years on it, much of it doing primary source research in France. After Joan of Arc, I would think it impossible for Mark Twain to have remained an agnostic.
You can get it free at Project Gutenberg- I just re-read it on my Nook.