I've reread this a few times over the past few years, but each time I feel the same: it's informative, but not enjoyable.
The author describes her audience as mid-experienced, which is a painfully narrow category. You're either going to a bored, reading what you already know; or overwhelmed with no point of reference for what she's talking about. Either way, the writing comes off as condescending.
I don't mind that she uses other artists' work- I think you'd have to show a range of examples. Unfortunately a lot of the portrait examples she uses are proficient, but not attractive as something to aspire to.