The Return to Narnia, as it is appropriately called, is the second in written order and the fourth in chronological order. It shows how the four Pevinses are pulled back into their favorite world by the blowing of Susan's horn, ironically.
When the four siblings return, they find that hundreds of Narnian years have past. The country is in ruins-especially Cair Paravel. The trees and talking animals have been silenced and humans rule the country.
The siblings eventually rescue a dwarf sentenced to die. Trumpkin is his name, and he proceeds to tell them everything that has happened and how Caspian came to blow Susan's horn.
King Miraz is a cruel dictator to his people, and he was teaching his nephew Caspian to be so as well. But Caspian had a nurse who taught him about old Narnia, as did his new tutor, a half human, half dwarf.
When Miraz's wife has a son of their own, Miraz proceeds to kill Caspian. But Caspian's tutor makes sure Caspian escapes from the castle into the woods, where he meets old Narnians in hiding.
The battle scene at the end of this book, in my opinion, is a copy of the first. However, the notion of Narnia changing after such a short time is interesting and inventive.
Lewis says he came up with the idea for this book by asking himself the question, "What if someone from that world called someone from this world instead of someone from our world going into that world?" And it worked.
It's good that C.S. Lewis did try different things with this series instead of the do the same thing over and over again. That's probably the biggest problem with series' today.