What was the title of C.S. Lewis’s 1933 allegorical novel about a journey through religious ideas?

The Pilgrim’s Regress was C.S. Lewis’s 1933 allegorical novel about a journey through religious and philosophical ideas. Its subtitle describes it as an allegorical apology for Christianity, reason, and romanticism.

The protagonist, John, leaves his home after becoming troubled by a burden and travels through a landscape filled with figures and places representing intellectual positions. Lewis modeled the broad structure on John Bunyan’s The Pilgrim’s Progress while adapting it to twentieth-century debates.

The book was Lewis’s first published work after his conversion to Christianity. It is less widely read today than Mere Christianity or the Narnia books, partly because many of its references are tied to the cultural arguments of its period. Lewis later added a lengthy explanatory preface.