Yes, there are heavy religious undertones in this children’s book. You do not have to look very hard. The Lion, the Witch and the Wardrobe is a fantasy novel for children by C. S. Lewis. Written in 1950, it is the first book of The Chronicles of Narnia and is the best known book of the series. These comments come from Wikipedia.org “The story takes inspiration from the Gospel themes of betrayal, death, resurrection, and redemption. The "Deep Magic from the Dawn of Time," and "Deeper Magic from Before the Dawn of Time" can be seen as similar to the Old and New Covenants of Christianity, respectively. In the subsequent books, there is a nod in the direction of the Trinity concept, with Aslan in the Christ-role and a passing reference to the "Emperor over the Sea" as God the Father. The children form a disciple-group around Aslan, with Edmund as Judas and Peter the High King as St Peter. The two girls also follow Biblical precedent, as Mary Magdalene and the other Mary, through being first to see the resurrected Aslan. In addition, there are various allusions to Christ's execution, including the humiliation prior to his death and the splitting of the curtain in the Temple, represented by the cracking of the stone table. The book is not intended to be a retelling of Biblical stories in another form; it simply borrows ideas from them so as to illustrate basic conceptions of Christianity (and some other ideas as well — Platonic philosophy among them). Additionally, the White Witch is said to be descended from Lilith, who some religious texts say was Adam's first wife. Edmund seems the character most close to the New Testament's Judas - but that unlike the original Judas, Edmund does not die or get consigned to eternal damnation, but is completely redeemed by Jesus/Aslan. Edmund also contains elements of the Apostle Paul.”

It's very allegorical, particularly in the sense that Aslan is a Jesus figure. He sacrifices himself to spare Edmund the sinner, then is resurrected. I remember seeing a lot of other parallels when I read it, but it's been so many years. The Lion The Witch and The Wardrobe was written as an allegory, and I think C.S. Lewis really didn't intend more books when he wrote it. The books that followed don't have near the religious parallels as The Lion the Witch and The Wardrobe because they more just focus on the fantasy world of Narnia and the capabilities of that environment, rather than re-telling a biblical story in a fantasy setting.