What was C.S. Lewis's first published work of fiction, released in 1933?

C.S. Lewis's first published work of fiction was The Pilgrim's Regress, released in 1933.

The full title is The Pilgrim's Regress: An Allegorical Apology for Christianity, Reason and Romanticism. Lewis wrote it after his return to Christian belief and modeled its broad journey structure on John Bunyan's The Pilgrim's Progress. The protagonist, John, travels through a symbolic landscape while encountering competing ideas and forms of belief.

The book appeared in 1933, before Lewis's better-known science-fiction trilogy and the Narnia novels. Its allegory reflects Lewis's intellectual concerns during the period when he was moving from atheism toward Christianity and trying to express that change in literary form.

The Pilgrim's Regress is not the same work as The Pilgrim's Progress. Bunyan's book was published in 1678, while Lewis's title deliberately echoes and reworks it for a twentieth-century setting of philosophical and religious debate.