Which C.S. Lewis book was published in 1940 as a study of human suffering?

The Problem of Pain was published by C.S. Lewis in 1940 as a study of human suffering.

The book examines why suffering exists if God is good and powerful. Lewis discusses divine omnipotence, human free will, sin, animal pain, hell, and the meaning of suffering within Christian theology.

It is an apologetic work rather than a memoir. Lewis approaches the subject through philosophical and theological argument, aiming to explain how suffering can be understood within a Christian account of creation and moral responsibility.

Readers sometimes connect the book with A Grief Observed, but the two works have different origins and tones. The Problem of Pain was written before Lewis experienced the death of his wife Joy Davidman; A Grief Observed records the personal anguish that followed her death and was published under a pen name.