Luna, Julie Anne Peters
Luna is the alias of a secret transexual boy named Liam. With the aid and support of his/her sister Regan, he continually transforms into his persona of Luna while hiding from his parents. In her attempts to protect her brother from discovery and his own depression, Regan slowly loses any life she has for herself. That is, until Liam decides to "transition" - to live his life as Luna and never again hide herself with his mask of Liam, even if it destroys his relationships with everyone he cares about.
Luna is a fantastic novel, one I'd recommend to anyone with an open mind. It does a wonderful job illustrating the struggles of alternative sexualities and the pressures it puts on their families, not to mention the expertly written, realistic, and lovable characters.