What was the title of C.S. Lewis’s 1933 autobiographical work about his conversion?

The Pilgrim’s Regress was C.S. Lewis’s 1933 autobiographical work about his conversion.

Subtitled An Allegorical Apology for Christianity, Reason and Romanticism, the book presents a symbolic journey through ideas and beliefs. Its title deliberately echoes John Bunyan’s The Pilgrim’s Progress, but Lewis’s work is not a sequel. Instead, it uses allegory to describe his own intellectual and spiritual movement toward Christianity.

Lewis had returned to Christian belief in the early 1930s after a period in which he identified as an atheist. He later described his conversion as involving both his reason and his imagination. The Pilgrim’s Regress was his first published work after that conversion and appeared in 1933.

Surprised by Joy, published in 1955, is Lewis’s more direct spiritual autobiography, which creates a frequent mix-up. Mere Christianity developed from wartime BBC broadcasts, while A Grief Observed concerns grief after Joy Davidman’s death. Each book has a different purpose and form.