Following up on our C.S.Lewis Today conference, I'm doing some reading on Lewis and atonement. The question has always been whether Lewis continues the view of Origen (3rd C) that Jesus' death was a ransom paid to Satan. In The Lion, the Witch and the Wardrobe, Aslan is a ransom, presumably to the White Witch, to pay the penalty for Edmund's rebellion (they call it the Deep Magic).
There's an interesting essay on this in The Chronicles of Narnia and Philosophy. The authors defend the Ransom theory, saying it is less offensive when Satan is viewed not as a person, but as pseudo-personal (like a mutant?). N.T.Wright says something similar here. It also helps if God and Satan aren't considered to be 'doing a deal', like business colleagues. I'm still pondering all this.
In this same essay, the writers speak of sinning as a loss of freedom, becoming "a slave to booze, sex or eBay". I love the way eBay has replaced rock and roll in this triumvirate of vices!