A theological book by C.S. Lewis, adapted from a series of BBC radio talks given by Lewis during World War II. It presents a reasoned case for the truth of Christianity, covering topics such as the moral law, the nature of God, and the Christian virtues.
Lewis makes this argument from desire that you mentioned.
""C.S. Lewis was mentioned in the context of his 'argument from desire' and later in relation to his studies on universal moral assessments. 'Mere Christianity' is a foundational work where Lewis articulates many of these arguments, including the moral law, making it highly relevant to the discussion of objective morality and human desire for transcendence."