The second book in C.S. Lewis' series The Chronicles of Narnia; also refers to the title character (see also King Caspian).
A year (our time) after the events of The Lion, the Witch, and the Wardrobe, Peter, Susan, Edmund and Lucy find themselves transported to Narnia again -- a thousand years after they knew it. They soon discover that Caspian and his allies have called the four kings and queens from Narnia's golden age to help them overthrow King Miraz the Usurper.