Hi, sorry, I wasn't being sarcastic at all. I meant every word sincerely and literally, including the questions. At first I thought I had no answer for "what do folks get out of Zinnser's book specifically?", but while writing my comment I discovered that I did! Sure, it wasn't very friendly, sorry for that. I was trying to help your prose. It seemed you mostly didn't like On Writing Well for its being a book, when you got much more from courses and their feedback.
I will admit I am expressing a subjective preference, not an objective indictment of Zinsser (I did get some value out of the first few chapters). Perhaps this dissenting opinion didn't need to be expressed because in retrospect no value was added because I didn't provide specifics myself (though I could -- I'm happy to make the case). And it's possible that I'm being unfair to the work. So in light of that, I withdraw my statement. But I still don't appreciate your sarcasm.