This is my least favourite of the Narnia books, simply because it's also the least relevant. Why are all four Pevensies back in Narnia anyway? At least The Horse and his Boy (arguably the most underrated Narnia novel) is interesting because Lewis introduces the Calormenes, who are critical players in The Last Battle. But Caspian
has nothing worth noting.
The main purpose of this book, I think, is to introduce Caspian so we're more familiar with him in The Voyage of the Dawn Treader. However, Dawn Treader is a much better book, so you may as well skip this one entirely.
Last question: WHY did they adapt this one into a film? Out of the seven novels, The Lion, The Witch and the Wardrobe, Dawn Treader, Silver Chair and Last Battle are begging
for movie adaptations. NOT the other three.
Not much to see here; move along to Dawn Treader and have some real fun!