Prince Caspian: The Return to Narnia (The Chronicles of Narnia #4) by C. S. Lewis

The Pevensie siblings travel back to Narnia to help a prince denied his rightful throne as he gathers an army in a desperate attempt to rid his land of a false king. But in the end, it is a battle of honor between two men alone that will decide the fate of an entire world.

Prince Caspian is the fourth book in C. S. Lewis's classic fantasy series, which has been drawing readers of all ages into a magical land with unforgettable characters for over sixty years. This is a stand-alone novel, but if you would like to read about more Narnian adventures, pick up The Voyage of the Dawn Treader, the fifth book in The Chronicles of Narnia.