The Lion, the Witch, and the Wardrobe is recognized around the world as classic children's literature. C.S. Lewis wrote it for a child audience and dedicated it to his goddaughter, Lucy Barfield. It's written in simple, straightforward prose appropriate for children, and, just in case you still weren't sure, the subtitle is A Story for Children.
In addition to being a children's book, it's a rollicking adventure story in which our heroes set out on a quest to recover their kidnapped friend and end up ruling the land. It's also clearly a fantasy novel—the presence of mythical creatures like fauns, dwarves, and talking animals might have tipped you off to that one.