Which C.S. Lewis book is an autobiography about his conversion to Christianity?

Surprised by Joy is C.S. Lewis’s autobiography about his early life and conversion to Christianity. Published in 1955, it traces the intellectual and imaginative experiences that influenced his changing beliefs.

The book describes Lewis’s childhood, education, service in the First World War, and academic development. It also discusses “joy,” Lewis’s term for an intense longing or desire that he regarded as pointing beyond ordinary experience. His return to Christian belief occurred gradually, with important conversations involving fellow Oxford writers J.R.R. Tolkien and Hugo Dyson.

The book is not a complete day-by-day spiritual diary. Lewis presents selected memories and ideas, and he discusses his conversion in relation to literature, mythology, and philosophy. A Grief Observed, by contrast, is his later account of bereavement after the death of his wife, Joy Davidman.