Which C.S. Lewis book first introduced readers to Narnia in publication order?

The Lion, the Witch and the Wardrobe was the first C.S. Lewis book about Narnia published for readers. It appeared in 1950 and introduces the Pevensie siblings, who enter Narnia through a wardrobe.

The story centers on Narnia’s endless winter under the rule of the White Witch. The children meet Aslan, the great lion and rightful ruler, and become involved in the struggle to restore Narnia. The novel combines adventure, talking animals, mythical creatures, and Christian symbolism.

Lewis later wrote six additional Narnia books. The Magician’s Nephew is earlier in Narnian history and explains the world’s creation, but it was published later, in 1955. That distinction between publication order and chronological order is the main reason readers sometimes name The Magician’s Nephew incorrectly.