First off, I did not read this book cover-to-cover but rather jumped around to the sections that seemed pertinent to myself and which I could relate back to my family. Some of the birth order factors make sense and has helped me to understand some family dynamics but as the book regularly points out, people's personalities (and hang-ups) are not just explained by birth order. There is the family environment of emotional, economic, etc support, as well as the spacing between children that play a role in personal development, of which no one can ever fit these factors/outlines exactly.
It's publication in 1976 makes for an interesting read about the social mores and norms of the time, especially as I am product of the next decade. The way Dr. Forer relates some of her therapy cases makes me wish that if I ever do need extensive therapy, I would like a therapist as clear-sighted and understanding as her. Not being a parent yet, I cannot comment on the effectiveness of the 'Parenthood' chapters but they do make me wonder about the development of those families I know with children.