What was the title of C.S. Lewis's autobiographical book about his return to faith?

C.S. Lewis's autobiographical book about his return to faith is titled Surprised by Joy.

Published in 1955, Surprised by Joy describes Lewis's intellectual and spiritual development from childhood through his return to Christianity. The book discusses his early experiences, education, literary interests, service in the First World War, and movement from atheism toward belief.

The title refers to Lewis's idea of “joy,” a sudden longing or intense desire that he associated with experiences of beauty, literature, and imagination. He distinguished this joy from ordinary happiness because it was marked by a sense of longing that could not be fully satisfied by the immediate experience.

The book is autobiographical, but it is not a complete day-by-day life story. Lewis concentrates on the development of his thought and religious outlook. His later marriage, for example, is not covered because it took place after the period described in the book.