Prince Caspian was excellently done. The special effects were some of the best I have seen (I was not impressed with the S.E. in the first film, but this has improved tremendously.). The characters–particularly King Peter–had a lot more depth than the book provides; the characters were 3 dimensional and believable.
There were several additions to the film that were not in the book. However, most of them were done well (I thought the Susan-Caspian romance was lame and unnecessary.). Even the castle battle scene fit with the flow of the book, which referenced such a battle without ever going into detail.
What I didn’t enjoy were the parts let out. In the book, the Telemarines are not defeated by skills on the battlefield, but by the playfulness of children “frolicking” with the Great Lion through the towns and countryside of Narnia. Crowds of people, nyads, & dryads dance around Aslan and Bacchus on his donkey as water turns into rivers of wine, buildings become flowers, and the sick and elderly are miraculously healed to join in the romp.
C.S. Lewis did a masterful job of turning “dark” Narnia into a place of laughter and joy in the final chapters of the book. The film seemed more intent on making it about battles and war, even having Peter behead an enemy.
Had I never read the book, I would give this film an A. But being familiar with the masterpiece, I have to give it a B for straying too far from the original intent/storyline.