In the intro to the edition I read, author Lois Lowry invokes Amy Carter (living at the White House at the time of the book's original publication), who influenced the character of Anastasia with her forthrightness. Anastasia is ten, and, at this point an only child. Her mother is an artist, and her father is a poet and Harvard professor. She keeps a diary that is a bullet journal forerunner, where she maintains lists of loves and hates, and other things. Over the course of the book, items move from one column to the other, as Anastasia experiments with things like pumpkin pie and getting a nice phone call from a former object of her hatred. Or maybe having to confront some things about herself, as when she learns her mother is pregnant. 

Oh, Anastasia! This is how it is for kids in certain kinds of families. Or maybe all? You're lead to believe you're the most important person in the world, and it's kind of a shock when you learn that you're not. She may not be the most important kid in the world, but she is a distinct children's book heroine.