Published in 1951, this was the second book that Lewis released in the Chronicles of Narnia series, and we recommend you read it second, just after The Lion, the Witch, and the Wardrobe. Chronologically, however, it is the fourth title, and is typically labeled #4.
It is the end of the holidays, and Peter, Susan, Edmund, and Lucy are heading back to school. As they wait at a railway station for their trains, Lucy feels an odd sensation, as if someone were pulling or dragging her somewhere. Soon the other children feel it, too. Almost before they realize what's happening, they find themselves standing in a strange wood.
The four children explore their surroundings and discover that they are on an island. They also discover the ruins of Cair Paravel, the castle where they had reigned as kings and queens in Narnia. As they puzzle over the apparent passage of years in Narnia, a boat approaches the island. Two soldiers have come down to the sea to drown their prisoner - a Dwarf. The children drive away the soldiers and rescue the Dwarf who tells them the story of Prince Caspian.
When Caspian's parents died, Miraz, Caspian's uncle, assumed the throne, to rule until Caspian grew old enough. But when Miraz has a son and heir of his own, he seeks Caspian's death. Caspian flees into the wilderness where he encounters a pair of Dwarfs and a talking Badger - creatures who inhabited Narnia before Narnia was conquered by the Telmarines, Caspian's people, and driven out by Miraz. There are many of the Old Narnians living in hiding, but with Caspian on their side, they seek to overthrow Miraz and drive the Telmarines from Narnia.
Caspian gathers an army of Old Narnians, but Miraz learns of their plans and sends his own armies to search for them. When Caspian's army suffers a series of setbacks, Caspian decides to blow the Horn of Queen Susan which he believes will bring help - possibly in the form of Aslan, the Great Lion, himself.
Trumpkin, the Dwarf, concludes his story to Peter, Susan, Edmund, and Lucy, explaining that he has been sent by Caspian to Cair Paravel to see if any help has arrived, and he is dismayed to discover the four children instead. Peter, Susan, Edmund, and Lucy quickly convince Trumpkin that they were once kings and queens in Narnia, and that the Horn has apparently called them back to Narnia to help Caspian.
The children and the Dwarf undertake a journey through the wilderness to meet Caspian and his army and lend their help. But the land has changed since they were rulers in Narnia, and the journey is difficult. Then Lucy claims to have seen Aslan. Could it be that the Great Lion, himself, has returned to lead the Old Narnians to victory? The other children are unsure, and Trumpkin will not believe in stories about magical Lions. Their doubt and disbelief nearly cause disaster when the children encounter one of Miraz's outposts. Only by taking a step of faith do the children find their way to Caspian.
But Caspian and the Old Narnians aren't out of danger yet. One of their own party has a dark plan for defeating Miraz, a plan that would lead them from one evil to another. Only the return of the Lion will set things right again.