The language is obviously dated- the book was published in 2005, and even before that, Kailey came out and began his transition in 1997, at 42 years old. The language of his generation at the time of writing is what many trans people would view as offensive or incorrect now. Some of the medical aspects of transition he writes about are dated too. Keep this in mind while reading.
There are a lot of good messages to trans people in general as well.
"It might sound strange to take pride in something that has nothing to do with winning the Nobel Prize, saving a life, or discovering the cure for cancer, but cultivating self-pride is an important step for people who have been shunned, ridiculed, and basically treated just downright nastily for a long time. I've been called "sick" and I've been called "brave," but I don't believe I'm either. I'm just a person struggling to get by in this world, like everyone else, while dealing with life's little practical jokes. In my case, one of my issues, besides the fact that there's never enough money, that I'm getting older every day, and that mechanical things always break down, is that I'm a transsexual. It never goes away, just like impending death and yearly taxes. It's not a curse and I'm not a victim. It's just a fact.
We don't know why some people are trans. Maybe we'll never find out, and if we don't, does it matter? It's simply the way some people are, whatever the reason, and by taking pride in ourselves, we can take back the power that has been siphoned away from us, pick ourselves up, dust ourselves off, and move on. Let's get over it, already. The choice is ours."
-Page 113, chapter "A Matter of Choice"
Kailey was truly an amazing trans elder, who passed away at age 59 in 2014. He was a staunch advocate for trans rights and recognition, but also a lot of 'radical' opinions for someone in the 90s and early 2000s- the recognition of people outside the gender binary, the encouragement of gender non-conformity even among binary people, and the acknowledgement not everyone wants to transition or needs to transition in the same way, especially not medically. He was a very important voice for all of us. R.I.P.