It's basically something like the Devil's Dictionary with a focus on standard fantasy tropes. I was hoping for something more like a guide in the sense of a real travel guide, rather than what is mostly a set of parodic definitions.
Certainly some of the commentary/implied definitions are spot-on, and point up some of the weaknesses of what is commonly called EFP (Extruded Fantasy Product). A lot of them, though, seem more specific to some particular subgroup of these which I've never read (the "Gay Wizard" bit, for instance, is totally out of left field; I can't think of a single example), and others seem to refer to "problems" which are more a matter of stylistic or practical choice than anything else. (questions of the "ecology" of the world, for instance; many writers -- myself included -- often aren't going to include details on flora and fauna unless it's germane to the plot, so you will see very few, if any, creatures described in the text unless they're something to eat, or something to fight.)
Overall, I found it a lightly amusing read but hardly anything that struck me as the "must read" book which it is often touted as. It's not clear enough on the whys and wherefores of the problems it attacks to be something useful to those who don't already know they exist, nor is it nearly as funny as it might be; perhaps the most hysterically funny treatment of most of the central problems of EFP *and* bad SF is "The Well-Tempered Plot Device" (by Nick Lowe back in '87; there are copies all over the web, the first I found was at http://news.ansible.co.uk/plotdev.html).
So, it's not bad, but I don't see the fuss.