Which C.S. Lewis book describes his return to Christianity?

Surprised by Joy is the C.S. Lewis book that describes his return to Christianity.

Published in 1955, Surprised by Joy is an autobiographical account of Lewis’s intellectual and spiritual development. It traces his experiences from childhood through his education, his growing interest in mythology and literature, and his movement from atheism toward belief in God and Christianity. The book’s title refers to Lewis’s idea of “Joy,” a powerful longing or desire that he associated with experiences of beauty and transcendence.

Lewis’s conversion was gradual rather than a single simple event. He returned to belief in God in 1930 and later became a Christian, influenced partly by conversations with fellow writers such as J.R.R. Tolkien and Hugo Dyson. Readers sometimes confuse this memoir with Mere Christianity, which developed from wartime radio broadcasts and presents arguments for Christian belief rather than telling Lewis’s life story.