Which C.S. Lewis book introduces the world of Narnia in publication order?

The Lion, the Witch and the Wardrobe introduces Narnia in publication order.

C.S. Lewis’s novel was published in 1950 as the first released installment of The Chronicles of Narnia. It follows Peter, Susan, Edmund, and Lucy Pevensie after Lucy discovers a passage through a wardrobe into a magical land. There they encounter the White Witch and the lion Aslan.

The Magician’s Nephew is earlier in Narnian chronology, because it tells the creation of Narnia, but it was published later, in 1955. This distinction explains why readers sometimes give that title as the first book. Publication order and internal chronology are different ways of reading the seven-book series.