This is my favorite book of the series so far, it's full of cool mini-plots, crazy adventure and Christian symbolism.
The protagonists are trapped in Calormen, a country depicted as a middle eastern desert with Sultans and Camels. They are desperate to leave into a foreign, almost legendary, land called Narnia, where there are springs, trees and even talking beasts. In this tale, Narnia represents hope, a place worth having an adventure through an unforgiving land.
By this point, there is no further evidence needed to understand that Aslan is a representation of God. The heroes are attacked and also saved by a Lion in more than one occasion and it's clear at the end that whatever happens that lead you to where you belong its God's will. God will chase you out of the places you are not supposed to be. God will take care of you when you feel lonely. God will push you to your limits so that you can conquer your fears and achieve what you must.
This story happens between the first 2 movies and feels like it's setting up for something bigger in the future.
The boy is a good and humble character and the horse is very funny.