K.S. Lewis (1898-1963) is a modern classic of English literature and a Christian thinker. His apologetic work “Mere Christianity” is written on the basis of a cycle of radio conversations. Christianity is already two thousand years old, and each of the three major and vast many small currents added to it their traditions and understanding of their ideologues. But under the traditions and differences in understanding, the essence of all Christianity is one. And she, this essence, which is to communicate with God, remains the same. Clive Lewis, who gives a clear and precise understanding of Christianity, turns to her. If you define the book briefly, then this is the answer to the question of what is Christianity. And the answer is complete and exhaustive.