What is the author trying to say in this story? What is his lesson in life

One of the basic components of Christianity in general and of Christ’s passion in particular, and therefore of this book’s metaphoric exploration of the latter, is the concept of redemption – specifically, the idea that a person’s sins, flaws, mistakes, or bad choices can be redeemed by an act of selflessness, compassion, or courage. In the story of Christ’s passion, and indeed in the story of Christianity, Christ’s sacrifice of his life is portrayed/seen as the ultimate act of selflessness and/or compassion, intended to redeem the entire human race (so the teachings go) from its life of sin. That spiritual narrative, that experience of faith in God and the ultimate good, and that demonstration of courageous compassion (or compassionate courage) is clearly and vividly echoed in the story of Aslan and his sacrifice to save not just one boy (Edmund) but what seems to be an entire land (Narnia) from the destructive forces of betrayal. They are also echoed, on a somewhat smaller scale, by Edmund’s subsequent act of courageous and potentially fatal self-sacrifice in fighting to destroy the Witch’s magic wand. There is the sense in Edmund’s actions that being redeemed triggers the need to perform the same kinds of actions. This again is arguably one of the cornerstones of the Christ story, and therefore of Christian teaching and philosophy – the idea/principle that redemption in the self triggers the capacity to redeem others.