Reading Adoption: Family and Difference in Fiction and Drama by Marianne Novy
A literary scholar who is an adult adoptee delves into one of the enduring themes of literature—the child raised by other parents
Marianne Novy is Professor of English and Women’s Studies at the University of Pittsburgh. She is author or editor of numerous books, including Imagining Adoption: Essays on Literature and Culture.
Harlow's Monkey 
It’s fascinating how often the theme of adoption is present in literature and myth.
One of my favorite stories as a child was of Momotaro, the Peach Boy, who was adopted by an elderly couple (popular Japanese folktale).
Recently I looked up the story on Wikipedia and was astonished to discover that Momotaro’s adoption might have been a late 19th century addition.