Which C.S. Lewis autobiography describes his return to Christian belief?

C.S. Lewis’s autobiography describing his return to Christian belief is Surprised by Joy.

Published in 1955, Surprised by Joy recounts Lewis’s intellectual and spiritual development from childhood through his conversion to Christianity. It discusses his early imaginative experiences, education, military service, friendships, and changing views about religion.

The title refers to a recurring experience of intense longing that Lewis associated with moments of beauty, literature, and imagination. He had returned to Christian belief by 1931, after years in which he identified as an atheist and later as a theist.

Surprised by Joy is not a complete account of every part of Lewis’s life. A Grief Observed, for example, deals with the aftermath of Joy Davidman’s death, while Mere Christianity presents Christian arguments rather than autobiography. The title also echoes the poet William Wordsworth’s use of the phrase “surprised by joy.”