Caspian returns for his second appearance in the Narnia chronicles, following his revolt against his evil uncle Miraz in the previous book, Prince Caspian. Now King of Narnia, Caspian has been ruling for three years, and he claims that in that time he's completely fixed all the social problems of his nation. Now that's impressive. He tells Lucy and Edmund that "There's no trouble at all now between Telmarines, Dwarfs, Talking Beasts, Fauns and the rest" (2.9). We feel a bit skeptical that it's possible to turn a country around so completely in just three years, but hey, this is a magical world who are we to question him? Besides, if there were still issues at home, it would seem pretty darn irresponsible of him to go gallivanting off on an adventure to find the end of the world.
As King of Narnia, Caspian has been reviving seafaring knowledge that died out during the last few decades. His purpose in building the Dawn Treader is to seek out the seven missing lords of Narnia – the only nobles loyal to his father, who were exiled by Miraz to prevent a rebellion. However, like his subject Reepicheep, Caspian is also excited by exploration for its own sake, and hopes to find the end of the known world at the edge of the eastern sea. In fact, by the conclusion of the voyage, his thirst for adventure will start to overpower his sense of responsibilities as King. His crew (and Aslan!) must remind him that he can't bail out on his country just to satisfy his own curiosity.
Caspian is a young king, but he's generally wise and thoughtful beyond his years. He is able to discern which advisors and lords are giving him good advice and surrounds himself with excellent councilors, such as Lord Drinian and Lord Bern. He's also able to resist the misleading, muddling bureaucracy and careless cruelty of Governor Gumpas. Caspian has a strong sense of ethics and reacts immediately against slavery, cruelty, and evil enchantments. Yet he is also proud and very conscious of his unchecked power as king. Occasionally we see him start to push the boundaries of his sovereignty, such as when he discovers the magical water on Goldwater Island:
"The king who owned this island," said Caspian slowly, and his face flushed as he spoke, "would soon be the richest of all kings of the world. I claim this land for ever as a Narnian possession." (8.78)
On this occasion it takes a cameo appearance from Aslan to bring Caspian to his senses. Similarly, toward the end of the book, when his friends and crew tell him he can't leave the ship and travel with Reepicheep to the edge of the world, Caspian reacts strongly: "'Can't?' said Caspian sharply, looking for a moment not unlike his uncle Miraz" (16.31). Once again, Aslan must step in and remind Caspian that with power comes responsibility. He can't just abandon his country.
On Ramandu's island, Caspian meets the woman who will become his queen – Ramandu's beautiful blonde daughter, who helps keep Aslan's table. From the moment he shows interest in her, Caspian starts to lose the narrator's attention. Something about this final step into adulthood means the narrator of the Narnia books is no longer interested in him, and in the next book, The Silver Chair, Caspian is entirely offstage.