NRO's Frederica Mathewes-Green discussed film adaptations in light of the recent Narnia film:
Movies that are better than the book they are based on:
1. Gone With the Wind.
2. The Godfather.
3. The Wizard of Oz.
4. The Princess Bride.
5. Jaws.
6. Forrest Gump.
7. Blade Runner.
8. The Lord of the Rings trilogy.
9. The Harry Potter series.
10. Adaptation.
Of the books I have read, yes to 4 and 7. A big no to 8 and 9. I've heard 6 is also inferior to the film and I can believe it.
The Princess Bride isn't that great of a book, it lacks the great style and atmosphere of the movie.
Do Androids Dream of Electric Sheep is good book, and in some ways it develops its themes better than the film, but it also lacks the depth and style of Blade Runners techno-noir.
But Harry Potter and the Lord of the Rings? No. The Potter movies lack the books depth of setting, pacing, and characterization. Each Harry Potter novel unfolds over an entire school year's time. The movies are badly rushed in comparison. The Lord of the Rings movies completely destroy most of the books' characterizations. Frodo is little more than an emo hobbit tossed by the winds of fate. Aragorn is the reluctant hero. The books are about hobbits braving horrors and the movies are about the great battles of men and elves. Not the same and not as good.
I haven't seen Prince Caspian yet, but it seems like the movie makes the same mistakes as the LotR films. The Pevensie's personalities are wrong. In the LWW movie, the kids are the reluctant heroes. In this latest film, Peter seems to be some sort of domineering bully. Contrast that with the books where the Pevensies are the children of prophecy. They don't become the kings and queens just because they're the first four kids to stumble along. They are also suited for those roles in a mythic sense. I love Prince Caspian the book, because these kids return as the heroes of legend and then they act like it. Even most of the Telmarines don't want to screw with them.
So sure, clean up some of the narrative ugliness by getting rid of the long flashback chapters, but at least get the characters right.