SPOILER ALERT because I'm talking about the last part of the book.
I'd actually give this 4.5 stars because this story was rocking and had me all the way in until the last 20% or so, when the focus shifted a bit, largely losing one of the main characters and the person who was the center of the start of the story.
As a woman of trans experience, the trans stuff feels pretty spot on. But the story is presented in the frame of the relationship between the two main characters. One kind of disappears in the end—and that left me feeling flat. The events felt true enough though.