I want to add that whatever my opinion of Maier might be, I don't think she was a narcissist, which is why the book is all the more uncomfortable. It's selling based on a presumption of her motivations and an intrusion of her character, rather than her ability as an artist. Also, the fact that she's a woman helps.
I don't think her gender or any other marketing ploy would succeed at selling her work to the extent that it has sold if she didn't have talent. And I really don't see how her gender plays into it either- her anatomical configuration has nothing to do with her photographic ability, which was obviously extraordinary.