Which C.S. Lewis book was published posthumously in 1964 as letters to a fictional friend?

Letters to Malcolm: Chiefly on Prayer was published posthumously in 1964 as letters to a fictional friend. C.S. Lewis died in November 1963, before the book appeared.

The work presents a sequence of imagined letters discussing prayer, worship, doctrine, doubt, and everyday Christian practice. “Malcolm” is not a documented correspondent in the same sense as Lewis’s real friends and literary associates; he functions as a literary device.

Lewis had worked on the manuscript during the final years of his life. The book therefore belongs to his late Christian writing, alongside works that explore faith through personal reflection rather than narrative fiction.

Readers sometimes confuse it with Letters of C.S. Lewis to Arthur Greeves, which collects real correspondence with Lewis’s lifelong friend. Letters to Malcolm is instead a constructed exchange, focused chiefly on prayer as its subtitle indicates.