I'm the co-author of the above book. I can confirm that it's a genuine user guide, aimed at getting people up and running with the Pi as quickly as possible - even without any prior Linux knowledge. It also contains sections on interfacing the Pi with other components and devices through its GPIO header.
More information on the book is available here: http://eu.wiley.com/WileyCDA/WileyTitle ... 6446X.html
(You'll notice that I'm not mentioned there - that's an oversight on Wiley's part: the bumph was written before I came on board, and hasn't been updated yet.)
Eben is heavily involved in the development of the book - he's responsible for the entire table of contents, meaning the book is what he as one of the primary developers of the Pi believes a user guide should look like - while I'm the one given the pleasure of putting words on paper.
To clarify a few points raised in this thread:
Unlike other Pi-centric books on Amazon, this isn't a scam or documentation cribbed from Wikipedia. It's a real user guide, developed by Eben and fleshed out by my own fair hand.
It's not just a paper copy of the SoC documentation from Broadcom. It's also aimed at a very
different audience - while a lot of the book will be welcomed by techie types (especially the GPIO section) it's designed to be accessible by all.
For the user who requested a Kindle version: the book is to be released in dead-tree, Kindle, PDF and ePub formats, although at present Amazon is only listing the dead-tree copy.
Any questions, let me know!