As it turns out, the mistake made in the book I was critical of is not alone in using fantasy to explain how harmonics are created from distortion. At the recent holiday book sale, I found another book on electronics, looked in the index for "harmonics," found the entry and read it. I burst out laughing, complete idiocy! Here is just a snippet.
"For example, theoretically speaking, a square wave contains all harmonics, but predominantly, odd harmonics"
Sounds reasonable, right? No, it's not. As my book points out, a square wave consists of harmonics based on a simple formula where the only variable is duty cycle. Duty cycle defines how much of the wave is high divided by the entire wavelength. A 50% duty square wave is high half the time, and low half the time, and has ONLY odd harmonics. Clearly the writer of the book never actually looked at a square wave or a spectrum of one, he was just making it up! Shouldn't we be allowed to point out mistakes in other people's books?