Fantasy:
* The Chronicles of Narnia: This series of seven fantasy novels is arguably his most famous work. It tells the story of children who travel to the magical land of Narnia and become involved in adventures with talking animals, mythical creatures, and the struggle between good and evil.
* The Space Trilogy: This series of science fiction novels explores themes of religion, philosophy, and humanity's place in the universe.
Christian Apologetics:
* Mere Christianity: A classic work of Christian apologetics, which presents a clear and compelling defense of the Christian faith.
* The Problem of Pain: Explores the issue of suffering and evil in the world.
* Miracles: A philosophical examination of the nature of miracles.
* The Screwtape Letters: A fictional correspondence between a senior demon and a junior tempter, offering insightful observations about human nature and temptation.
Literary Criticism:
* The Allegory of Love: A critical study of medieval romance literature.
* A Preface to Paradise Lost: An analysis of John Milton's epic poem.
Poetry:
* Spirits in Bondage: A collection of poetry exploring themes of faith, love, and loss.
* The Weight of Glory: A selection of essays and sermons.
Other:
* The Pilgrim's Regress: A spiritual allegory that follows the journey of a young man seeking truth and meaning in life.
* The Great Divorce: A story about a bus trip from Hell to Heaven, which explores the nature of choice and the consequences of sin.
It's important to note that: While Lewis is known for his Christian writings, he also wrote books that explore other themes and genres. His work often touches upon topics like philosophy, literature, and human experience.