This was quite a short book but it told a really interesting story about a girl's relationship with her transgender sister.
Regan's older sister, Luna, can only come out at night. Because by day, she's trapped in the body of Liam, a boy constantly under pressurre from the people in his small town to be more of a man, do sports and other gender-conforming crap.
This book really focusses on Regan's story and how Luna's transition affects her, as well as the stuff she's going through at school. Her family live in quite a small, gender-conforming town, so obviously that doesn't help them in the slightest.
As a character, Luna was quite underdeveloped, which was a shame considering the point of the book is her decision to transition and how this affects her relationship with Regan. And the only thing we really learn about Luna, is that she is totally and utterly self-obsessed, and yes, I know that makes me sound like a complete arsehole because transgender folk have to deal with a whole level of life-crap that I can't even begin to comprehend, but she was really annoying. She was like, 'It's all about me! ME! ME! ME!' I don't recall her showing a single shred of kindness towards Regan, other than when Regan was doing something for her.
So there. I'm a terrible human being.
NB - if you want a book about a transgender girl where the MC is totally relatable and just makes you want to weep, try If I Was Your Girl by Meredith Russo.
Because Luna is quite underdeveloped and the story is told from Regan's POV, I would hesitate to call this a trans book. We don't see anything of Luna's thoughts or hopes or fears - only how her transition affects Regan and forces her to deal with small-town smallmindedness.
There was also a really interesting relationship with Regan and Liam/Luna's parents - their mum has recently set up her own (successful) business and their dad is doing less well career-wise, so they are both challenging gender norms too.
Despite Luna's intense annoyingness, this was still a decent read. The plot rattles along quickly and the sparse narrative flows really well, so I ended up finishing it in an afternoon.