Humm ..... think in terms of a 2 semester course, Semester 1 and Semester 2 ... or one class in Basics and another in Advanced .... or ... after she wrote the first book she thought of some additional things to pass along ...
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain
Someone will correct me if I'm wrong, but If I remember correctly from her bio, FtW is right. There was a lot of specifics (for example, detailed baking was one if I'm right) that didn't "fit" in her first effort, so she went for II. What a woman.