I've decided to reread Prince Caspian. Voyage of the Dawn Treader and The Horse and His Boy were always my favorites, but I figured I'd start with the one with the movie out first and compare the two, as this movie was made with a pretty liberal hand on acuracy.
The kids are off to boarding school. I'm assuming the war is still on, though no one mentions it. Suddenly everyone is being tugged to Narnia. Conspicuously absent is the fight scene and chip on Peter's shoulder. Once in Narnia they set about wandering around an island and eating sandwiches. It's all rather boring.
The kids do some detecting and realize they're in Cair Paravel. It's actually Peter and not Lucy who figures this all out. After Susan chickens out about going down the dark treasure hole, Edmund whips out the flashlight of many plot points in the movie. They keep bringing up the fact that they might run out of battery, which makes sense. After rooting around for a while, they find their old gifts. It is explicitly mentioned that Edmund got nothing because he was being a big dillweed at the time. Susan wants her horse back.
Edmund comes to the conclusion time doesn't pass the same way in Narnia. The kids find a dwarf about to be drowned. Susan does some fancy shooting and the dwarf is dropped back into the boat, not the water, and the soldiers run away. The dwarf is a pleasant little thing named Trumpkin who is highly grateful for his rescuing and sets about explaining that he's a messenger for King Caspian, or at least that Caspian SHOULD be king. The Pevensies are all very confused and set in for some exposition. I realize Trumpkin is a massive departure from character.