C.S. Lewis's 1-Statement Summary of Each Narnia Story

The Chronicles of Narnia—

The Main Theme of Each Book, According to C.S. Lewis in a Letter He Wrote Back to a Young Inquirer

The Magician’s Nephew:  the Creation and How Evil Entered Narnia

The Lion, the Witch and the Wardrobe:  the Crucifixion and Resurrection

The Horse and His Boy:  the Calling and Conversion of a Heathen

Prince Caspian:  Restoration of the True Religion after a Corruption

The Voyage of the Dawn Treader:  the Spiritual Life (Especially in Reepicheep)

The Silver Chair:  the Continued War Against the Powers of Darkness

The Last Battle:  the Coming of the Antichrist, the End of the World, and the Last Judgment

Source Note: This comes from a letter written by C.S. Lewis March 5, 1961 to a 10-year old English girl named Anne, who wrote to him with a very intelligent question about Narnia. Her letter may be found under her married name, Anne Jenkins, in The Collected Letters of C.S. Lewis, volume 3. (There is also a separate book of Lewis's letters just to children.)  The BBC posted a story in 2006 where Anne tells how she made her special letter available to the public, and it shows pictures of the letter and envelope addressed to her, using her maiden name.