What is the author's tone in The Discarded Image: An Introduction to Medieval and Renaissance Literature by C. S. Lewis?

Lewis' tone throughout the book is scholarly. He is careful to cite sources for any historical or textual claim he makes and he backs up his argument with frequent quotation from primary sources. While the book is called an "introduction" to Medieval and Renaissance literature, it would be incorrect to think that it is a mere overview, one that is not arguing for a specific thesis. While Lewis does attempt to cover a large portion of Medieval belief—and, thus, in a way, it could serve as a mere overview—the purpose of his depiction of Medieval belief is to serve his thesis that Medieval literature and the worldview which it presupposed are something worthy of both modern research and respect.