Isn't that the first wide publication of the extant Bix letters? Seems to me reading Bix in his own voice is pretty revealing, if what you're interested in is the Bix biography. But I thought this book was something different, a sort of meta-biography, the story of the legend, the legion of admirers whose sheer numbers enable them to have taken over Bix Inc. over the decades. Not that they set out to, but that seems to be what has happened.
I haven't read it yet--looking forward to it, and to the discussion here.