Which C.S. Lewis book was published posthumously in 1964 under the title Letters to Malcolm?

Letters to Malcolm: Chiefly on Prayer was published posthumously in 1964.

The book presents an imagined exchange of letters about Christian prayer. Lewis addresses a fictional correspondent named Malcolm and discusses private prayer, communal worship, distractions, language, suffering, and the relationship between ordinary life and religious practice.

Lewis died on 22 November 1963, and the volume appeared the following year. It was one of the final works published under his name and was edited after his death. Unlike a systematic theological treatise, it uses the flexible form of personal correspondence, allowing Lewis to explore questions through brief reflections and examples.

The book is sometimes confused with A Grief Observed, which Lewis wrote after Joy Davidman’s death and published in 1961 under the pseudonym N.W. Clerk. Letters to Malcolm focuses primarily on prayer rather than bereavement and is not an autobiography.