The story takes place years after Nanny left her charge, Grayer X. She and her husband have just moved back to New York after being abroad, and Grayer shows up drunk on their doorstep wanting some explanations. And thus she becomes embroiled in the X family troubles all over again, while dealing with her own marriage and life decisions.
Also proving that I am their target demographic was Nan's running concern about whether or not to have children. And if yes, then when? She struggles with the question, saying to her mother:
"I want to hear it's all going to be okay."
"Well, of course it's going to be okay. It just might not include
Further, I feel like in the first book, Nan was such a do-gooder and firmly on the right side of things (which I guess she was, if you're comparing her to Mr. and Mrs. X) and in this book, people call her out on her righteous indignation. I liked that. She comes off as a know-it-all but doesn't always get away with it. (Maybe I'm mis-remembering the first book but the point remains.)
So in the end I found the book to be more interesting than I had anticipated. A nice surprise.