Which C.S. Lewis book presents Christian virtues through the allegory of a medieval pilgrimage?

The C.S. Lewis book that presents Christian virtues through a medieval pilgrimage allegory is The Pilgrim’s Regress.

Lewis published The Pilgrim’s Regress in 1933, making it his first published work of prose fiction. Its full title refers to an allegorical apology for Christianity, reason, and romanticism. The title deliberately echoes John Bunyan’s The Pilgrim’s Progress, another famous Christian allegory.

The protagonist, John, travels through a landscape populated by symbolic figures and encounters ideas, temptations, and rival philosophies. The journey reflects Lewis’s own intellectual and spiritual development, including his movement from atheism toward Christianity.

The book is more explicitly philosophical and difficult than The Chronicles of Narnia. It is also distinct from The Great Divorce, which uses a fantastical journey to explore heaven, hell, and human choices. Lewis revised The Pilgrim’s Regress for a later edition and added a discussion explaining some of its symbols.