Two of the familiar Pevensie children literally fall into Narnia with their (rather horrible) cousin. They are rescued by Caspian, who is journeying through unknown seas to find seven men loyal to him, who were exiled many years earlier. But he, along with others on board, hopes that the journey will culminate in finding the end of the world.
They have a series of adventures – slavers, dragons, a sea monster, and Deathwater Island – which can be enjoyed as adventures or as tales of hope and faith and compassion. In that sense, it's a little like a more-exciting and Christianised The Little Prince.
Free Sample (from the start):
There was a boy called Eustace Clarence Scrubb, and he almost deserved it. His parents called him Eustace Clarence and masters called him Scrubb. I can’t tell you how his friends spoke to him, for he had none.
Rating: PG. I’d call it absolutely G and safe for anyone, but one character is a close parallel to Jesus Christ (in one of the later books this character clearly states that he exists on Earth as well, is known by a different name there, and that the children have been brought into Narnia so that they can more easily recognise him on Earth), and some atheists have found that offensive. The books do focus on the adventures, rather than allegory about 95% of the time.