There was already a Nikon D400 book listed on Amazon Germany a year ago. The publisher came out officially and said that this was a mistake. Few months later they released the same book (same ISBN) with a Nikon D300s name instead.
Now we have a new Nikon D400 book listed on Amazon Germany (from a different author: Klaus Kindermann).
The "product details": 320 pages, there is date reference of May 2010 (ISBN-10: 364560037X, ISBN-13: 978-3645600378):
The publisher is Franzis Verlag - could not find any other information on their website.