My review: 4 out of 5 stars - I liked it, it made some changes from the book but I thought it stuck with the main themes very well.
Here is another positive review (not yet on the web - I will add it soon).
Here is a more negative review.
Other thoughts on Prince Caspian...
SETTING THE SCENE
In a dreary train station in England on their way back to boarding school, Peter, Susan, Edmund, and Lucy suddenly feel themselves being tugged into another world. They arrive on an unknown island, where they find the ancient ruins of a palace. But something feels familiar about this place. Eventually the children recognize that they are at Cair Paravel, where they themselves ruled as Queens and Kings of Narnia. They discover that they have been called back to Narnia because the forces of Old Narnia are in trouble. Just one year has passed in our world, but a thousand years have passed in Narnia. The rightful king, Prince Caspian, is fighting a war against his uncle, King Miraz, who wants to destroy the country of Aslan—the Talking Beasts and trees, the Dwarfs and Fauns—and all memory of Old Narnia. In desperation, Caspian has blown a magical horn—the very horn Susan once received from Aslan—to summon the Lion and the children to help them in their struggle.
Some of the themes in Prince Caspian are: God calling people to the place where they are needed, the faith of Lucy (youngest), everyone having different gifts that are all needed, the need for courage in the face of evil, the recurrence of the power of evil and the ultimate victory of God (good).
“Everything you know is about to change.” – Aslan (Movie)
"Welcome, Prince," said Aslan. "Do you feel yourself sufficient to take up the Kingship of Narnia?" "I — I don't think I do, Sir," said Caspian. "I'm only a kid." "Good," said Aslan. "If you had felt yourself sufficient, it would have been a proof that you were not." (Book & Movie)
"Spiritual style rather than doctrinal proposition is important because Lewis, according to his own account, wrote in a spirit of play, casting "all these things into an imaginary world, stripping them of their stained-glass and Sunday School associations," in order to show what it feels like to be a believer—to smuggle religious emotions "in their real potency" past the "watchful dragons" of boredom and embarrassment. He was not writing allegory, which shows us what is true, but fairy story, which shows us what is desirable.
When critics reduce Lewis's fairy stories to allegory, they diminish the specific literary pleasure for which the stories were designed and obscure the masterly portrayal of religious feelings at different stages in life. These stages become clear as we examine the books in order.
For children born into an Anglican-style religious home, the first awareness of Christianity comes through its two great festivals, Christmas and Easter. The young child does not know why these holidays are so important; he simply accepts the joyous celebration, feeling it more as a physical than a mental or spiritual event. This is exactly what we find in Wardrobe, the first Chronicle. The arrival of Father Christmas in Narnia is a lovely surprise for the children, a physical experience of receiving presents and having a good dinner. Mr. Beaver understands the evangelium of Asian on the move, of an end to the always-winter-but-never-Christmas stagnation, but the children are less aware of it.
The Narnian analog of Easter also focuses on physical sensations: the delicious languor of the spring thaw; the cold, horror, and weeping of the girls' vigil; the joyous resurrection-morning romp and lion-back ride. These, rather than a cognitive grasp of the theology of incarnation and sacrificial redemption, are the focus of Wardrobe. It is Christianity on the very simplest level." (from “The Compleat Anglican: Spirit Style in the Chronicles of Narnia” by Doris T Myers, 1984)