When a boy wrote to C.S. Lewis, worried that he loved Aslan the lion more than he loved Jesus, Lewis told him something you would never expect...
Instead of saying the lion was just a character in a book, he told the boy he could not possibly love Aslan more than Jesus. Because Aslan is not a symbol for Christ: according to Lewis himself, Aslan IS Christ.
This is the thing most readers get wrong about Narnia. People call it an allegory, a tale where a lion stands in for Jesus the way a character might stand in for an idea.
Lewis rejected that completely...
In a letter he wrote: "If Aslan represented the immaterial Deity, he would be an allegorical figure." Instead, he explained, Aslan is the answer to a question: "What might Christ become like if there really were a world like Narnia, and He chose to be incarnate and die and rise again in that world as He actually has done in ours?"
The answer Lewis gave was a lion. And he explained exactly why: "Since Narnia is a world of Talking Beasts, I thought He would become a Talking Beast there, as He became a man here. I pictured Him becoming a lion," Lewis wrote, partly because the lion is the king of beasts, and partly because "Christ is called The Lion of Judah in the Bible."
Once you know this, the story of Narnia changes: the moment Aslan lays down his life on the Stone Table for a traitor, and rises again at dawn, is not like the story of Christ. To Lewis, it is that story, happening in another world. And it is why, in the final chapter of The Voyage of the Dawn Treader, Aslan tells the children this:
"I am in your world too. But there I have another name. You must learn to know me by that name. This was the very reason why you were brought to Narnia, that by knowing me here for a little, you may know me better there."