Which medieval allegory did C.S. Lewis publish in 1933 after returning to Christian belief?

C.S. Lewis published the medieval-style allegory The Pilgrim's Regress in 1933 after returning to Christian belief.

The book follows a character named John who travels through a symbolic landscape while seeking the source of an oppressive burden. Its title deliberately recalls John Bunyan's The Pilgrim's Progress, but Lewis's work is shaped by debates about modern philosophy, culture, and theology.

Lewis described it as an allegorical apology for Christianity. The story presents ideas and intellectual movements through names and locations, allowing readers to encounter arguments in fictional form rather than as a conventional essay.

The book appeared soon after Lewis's conversion to Christianity, which developed through conversations and reading during the early 1930s. It predates his better-known apologetic works, including Mere Christianity and The Problem of Pain.