Which C.S. Lewis book was published in 1933 as his first major prose work?

The Pilgrim’s Regress was published in 1933 as C.S. Lewis’s first major prose work. Its subtitle identifies it as an allegorical apology for Christianity, reason, and romanticism.

The book follows a character named John as he travels through a symbolic landscape. Lewis designed it partly as a response to John Bunyan’s The Pilgrim’s Progress, but the work also reflects Lewis’s own intellectual and spiritual development. It was written soon after his conversion to Christianity.

Lewis had already published poetry under the name Clive Hamilton, including Spirits in Bondage and Dymer. The Pilgrim’s Regress therefore marked a transition from verse publication to the prose apologetics and fiction for which he later became famous.

Readers sometimes confuse this title with Mere Christianity, which grew out of wartime radio talks and was published later. The Pilgrim’s Regress is also not one of the Narnia novels. It is a dense, explicitly allegorical work aimed more at adult readers and students of Christian ideas.