Very enlightening read, I really think everyone can learn something from it. My few complaints was how internalizer-focused it was. I felt like more focus could've been on externalizers. As she herself said, everyone falls on a spectrum. Another thing that bothered me was it was a bit stigmatizing, "emotionally immature" and "mature" was probably used for simplicity. Again, we all do fall on a spectrum. Even the most emotionally mature person has moments of immaturity. 

This book is a great starting point for learning to recognize emotionally immature behaviors in your parents (and yourself!), but it is very much a starting point. If you have been on this journey for any length of time quite a bit of it becomes redundant. 
The beginning felt like it was leaning "blame all your issues on your parents, don't worry about taking accountability for anything" but later chapters did start to dive into ways to make changes in order to be more emotionally mature / attract emotionally mature people into your life which was good. 
It relies heavily on anecdotes, which sometimes can be interesting, but often they were very surface level and repetitive. 
Again, this book was very much for the start of the journey. If that's where I was then I do think this book would have been more eye-opening for me. As it was, I still did learn and it was able to inspire some soul searching on my part. Especially the later chapters.