What was C.S. Lewis’s first published book?

C.S. Lewis’s first published book was Spirits in Bondage.

Spirits in Bondage: A Cycle of Lyrics was published in 1919, when Lewis was twenty years old. It was a collection of poems rather than a novel or work of Christian apologetics. The book appeared under the pseudonym Clive Hamilton, combining Lewis’s first name with a surname he used for literary publication.

The poems reflect themes including suffering, nature, war, doubt, and captivity. Lewis had served in the British Army during the First World War, and some of his early writing bears the marks of that period. The collection predates his conversion to Christianity by more than a decade.

Readers sometimes name The Pilgrim’s Regress as his first book because it was his first major work of fiction published under C.S. Lewis. That novel appeared in 1933. Spirits in Bondage came earlier and is therefore the correct answer when “first published book” means his earliest book publication.