Well, admittedly, I was trying to market the book, but had a very small space for the text, so I boiled things down to their lowest common denominator. In looking at it now I can see I oversimplified things. Surely there are several books that deal with the show's "world of witchcraft", though I think mine is the only one to really get into the nuts and bolts of the show's fiction, which is what I was trying to express. I appreciate your bringing that to my attention - it wasn't my intention to be dismissive toward the works that came before mine - and I will fix that up in future versions of the ad, and ads in general.