Sam Martin was browsing in a Boston record store 23 years ago when an unusual photography book caught his eye. Mr. Martin flipped through its pages, which featured portraits and interviews with women who had become men, and started to cry.

“I thought, ‘Oh, my God, I’m not the only one,’ ” said Mr. Martin, 43, who started transitioning to male from female after he bought the book. “When I was growing up, I never saw people like me in movies or books.”

Mr. Martin is now on a mission to change that. He belongs to a small group of emerging authors who are writing children’s literature that centers on transgender characters, hoping to fill the void they felt as young readers. Read More