Which C.S. Lewis autobiography describes his intellectual and spiritual conversion?

Surprised by Joy is the C.S. Lewis autobiography that describes his intellectual and spiritual conversion. Published in 1955, the book traces his development from childhood through atheism and toward Christianity.

Lewis uses the word “joy” for a powerful, fleeting longing that he associated with experiences of beauty, literature, and imagination. The autobiography follows how those experiences influenced his reading and thinking, rather than presenting a simple day-by-day diary of conversion.

His return to Christianity occurred in stages. Lewis moved from atheism toward belief in God in 1930, then became a Christian in 1931. His conversations with J.R.R. Tolkien and Hugo Dyson contributed to this process, especially discussions about myth and the Christian story.

Readers sometimes choose Mere Christianity because it explains Lewis’s Christian arguments, but that book grew from wartime radio talks and is not an autobiography. A Grief Observed is instead a record of grief after Joy Davidman’s death. Surprised by Joy is the work specifically devoted to Lewis’s personal intellectual and spiritual journey.