What was C.S. Lewis's final published fiction book?

Till We Have Faces was C.S. Lewis’s final published fiction book.

Published in 1956, the novel was Lewis’s last completed work of fiction. It adapts the Cupid and Psyche story from the Latin writer Apuleius, but its narrator is Orual, a queen whose personal grievances shape the way she tells events.

The book followed Lewis’s major works for children and his science-fiction trilogy. Its adult themes include possessive love, religious doubt, self-knowledge, and the painful process of recognizing one’s own motives.

The answer is sometimes confused with The Last Battle, which was the final volume published in The Chronicles of Narnia, or with That Hideous Strength, which completed the Space Trilogy in 1945. Till We Have Faces is the final published novel in Lewis’s overall fictional output.