As the release of The Lion, the Witch and the Wardrobe approaches, various people have been publishing reviews of CS Lewis' Chronicles of Narnia. One of the more insightful comments I've seen is by Alison Lurie, "writing in this Saturday's Guardian":http://www.guardian.co.uk/arts/features/story/0,,1656607,00.html:
It seems deeply unfair that Edmund, Susan's younger brother, who has betrayed the others to the Witch, is allowed to repent and remain King Edmund, while Susan, whose faults are much less serious, is not given the opportunity.
The contrast here is between the forgiveness that Edmund finds after repenting of his treachery in The Lion, the Witch and the Wardrobe, and the permanence of Susan's rejection of Narnia near the end of The Last Battle, which Lurie suggests may be the result of Lewis failing to think through the structure of his story carefully enough.
Rather than being confused, however, Lewis is at this point deliberately illustrating a very Christian contrast, between the forgiveness Jesus holds out to even the very worst person who turns away from their sin, and the rejection Jesus promises for those who finally reject him:
I tell you that any sinful thing you do or say can be forgiven. Matthew 12:31 (CEV)
The master will surely come on a day and at a time when the servant least expects him. That servant will then be punished and thrown out with the ones who only pretended to serve their master. Matthew 24:50-51 (CEV)
Jesus himself told a story about the jealousy that this free offer of forgiveness arouses in some people, in "Matthew 20:1-16":http://www.biblegateway.com/passage/?book_id=47&chapter=20&verse=1&end_verse=16&version=46&context=context. The idea of unmerited forgiveness does seem "unfair" to us, but it is also unfair to accuse Lewis of carelessness in this instance, where he is in fact being careful to follow what Jesus taught.