Which C.S. Lewis book begins with four Pevensie children entering a wardrobe?

The C.S. Lewis book in which four Pevensie children enter a wardrobe is The Lion, the Witch and the Wardrobe. It was published in 1950 as the first published Narnia story.

The children—Peter, Susan, Edmund, and Lucy Pevensie—visit the countryside during the Second World War and discover that a wardrobe opens into the land of Narnia. Lucy enters first, meeting the faun Mr. Tumnus; her siblings later follow and become involved in Narnia’s conflict with the White Witch.

The story introduces Aslan, the White Witch, and the recurring contrast between Narnian winter and renewal. Its plot includes betrayal, sacrifice, resurrection, and restoration, themes that have prompted extensive discussion of Lewis’s Christian symbolism.

The book is sometimes placed first in reading lists and sometimes after The Magician’s Nephew, depending on whether readers prefer publication order or Narnian chronological order. Regardless of sequence, it was the first Narnia volume readers encountered.