A literary theme is an idea expressed throughout a story. Historically we have seen several common themes portrayed in literature, many of which teach a moral lesson. Children's literary themes, in particular, focus on teaching young readers important lessons about relationships, values and how the world works.
Long, Hard Journey
One theme that commonly appears in children's literature is the hero embarking on a long, difficult journey. Sometimes the outcome of the journey is responsible for the fate of the entire world, as in the Lord of the Rings series by J.R.R. Tolkien. Similarly, the hero may try to help others by embarking on the journey, such as the little train in The Little Engine That Could which was bringing toys and food to the children on the other side of the mountain.
Other times, the heroes seeks personal gain as do the characters who travel together in The Wizard of Oz. The characters may escape from a difficult life as in stories like James and the Giant Peach. Stories about long and difficult journeys teach children the importance of perseverance and willpower when going after a goal.
Many children's stories feature a great battle. The battle may be between forces of good and evil, such as in the Harry Potter series. In other examples, the battle is simply between two entities who are after a common boon such as in The Last Battle, the last book of C.S. Lewis' The Chronicles of Narnia series when men and beasts fight for ownership of the land of Narnia.
Friendship & Love
Friendship and Love are commonly portrayed in children's literature. Shiloh by Phyllis Reynolds Naylor is the story of a young boy who goes to great lengths to protect his dog from abuse. Charlotte's Web is another story about the friendship, between a young girl and her pet pig.
Honesty & Deception
Stories featuring lessons about honesty are common. Pinocchio is about a puppet who wants nothing more than to be a real boy so that he will be loved by his maker. When Pinocchio lies, his nose grows. He faces troubles throughout the story because of this trait. The Boy Who Cried Wolf is another well-known story which focuses on the dangers of deceptiveness. The boy in the story lies so often that no one believes him when he is telling the truth.
Deception becomes a tool used by evil characters or "bad guys" to take advantage of the good. For example, in Hansel and Gretel a witch tricks the children into coming into her house so that she can eat them.