My child recently came out as non-binary and this book was recommended to me over and over. Then I saw that it is one of the most challenged books in the US and knew I absolutely had to read it. I am so glad I did. I am so thankful my public library has a copy (and it was prominently on display too, yay!)
It was really helpful for me to read the perspective of someone who questioned their gender identity and explored different options over time. It helped me understand the thought path that one might travel through this journey. Many of my questions were answered, and I walked away with lots of things to talk to my kid about. 
Most importantly, I got to hear in honest detail what it feels like to be someone who does not belong in the body they were born into. That is something I won't ever be able to understand, but now I at least have an idea of how someone lives through it.