I dont have a problem with a market idea as long as its used by community members
vs lets say sparkfun who only bothers to show up around here to promote their interest while we get to debug and support their half broken (and totally ripped off) crap every single day
(back on topic)
smiley, that looks like a great addition to what lit there is for the arduino, and I love that you can "test drive" the book on your site
looks well done!