This is probably the foundational book for my fantasy interests (the only other option is John Bellairs’s The Trolley to Yesterday, which is probably a book I loved more but its genre is a little harder to define).   As a child, the idea of opening a wardrobe and discovering an entirely new world was mesmerizing.  And the novel holds up so well, each scene captivating, building on the others.   The characters and their internal conflicts that define the external conflict in the story are well done and completely believable.  As a child, I didn’t notice or care about the religious allegory.  It works without it.