Which C.S. Lewis novel begins with the children entering Narnia through a wardrobe?

The Lion, the Witch and the Wardrobe begins with children entering Narnia through a wardrobe.

Published in 1950, the novel introduces Peter, Susan, Edmund, and Lucy Pevensie. Lucy discovers that an ordinary wardrobe leads to the land of Narnia, where the White Witch has imposed a long winter. The children become involved in the struggle to restore the rightful ruler, Aslan, and help end the Witch's rule.

The book was the first Narnia novel published, although later reading orders sometimes place The Magician's Nephew before it because that story describes Narnia's creation. The wardrobe itself became one of the most recognizable gateways in children's fantasy. Lewis dedicated the book to his goddaughter, Lucy Barfield, whose name inspired Lucy Pevensie's name.