This is an excellent example of a fan book. Just so you don't misunderstand, this is not an art book (I imagine one will happen sooner or later). It still contains many very nice illustrations.
Beside the illustrations, the book contains character guides, seiyuu interviews, staff interviews, production notes, episode guides, and more. I actually stopped reading the book in the middle because it contains information on episodes I have not watched yet. Seiyuu interviews start out clean, but even those start talking about later episodes, so I recommend DVD-only viewers to wait a bit before diving too deeply into this book.
