Children's Literature

What makes children's literature? Does a book become children's literature because of the author's intent in writing, or because of who the book appeals to? Robert Morpurgo was once the Children's Laureate for Great Britain. Some reviewers indicate that his stories are too sophisticated for children, but isn't that really the best children's book of all? One that appeals to children as well as the adults who read to children? I just read Morpurgo's Singing for Mrs. Pettigrew, memoir interspersed with short stories. The stories could be shared with children, but are appealing for adults as well. I had not read any of Morpurgo's work before this, but will keep my eyes out for his name now. Anyone heard of Why the Whales Came?