i bought that book for my 12 year son as a next step in broadening his view on Lego Mindstorm.. actually, i bought two books: Discovery and Inventor's Guide. While the first one is guiding people through the basis of the NXT equipments the Inventor's Guide is focusing on the applications of that knowledge. You can find some very interesting projects there, i.e. printer. The projects described there got me involved sometimes, too. Especially in the area of programming - adding more functionalities, adopting to our ideas..
Very nice book, lots of joy with following the projects there and broadening the view on possible applications..