The book 'T Middlesex' by Jeffrey Eugenides has elements where the main character is born with a genetic condition that leads to a change in gender over time, which can be considered a form of a boy - to - girl transformation in a sense. It's a complex and beautifully written story that delves deep into issues of identity, family, and self - discovery.
Another one could be 'Gracefully Grayson' by Ami Polonsky. Grayson is a boy who wants to be a girl. It shows his journey in school and at home as he tries to be true to himself and transition. It's a story that emphasizes the importance of acceptance and following one's true self.
There is also 'Luna' by Julie Anne Peters. In this book, the main character's sister is transgender. The story shows the journey of the sister who was born as a boy but is a girl inside. It gives a great insight into the struggles and the beauty of self - acceptance in such a situation. It's a heartwarming and eye - opening read.