C.S. Lewis' works have probably been as helpful to me as any other writings beside Scripture. The essay linked here, "On the Reading of Old Books," originally appeared as an introduction to Athanasius' On the Incarnation. Athanasius was a 4th century Christian who is credited as helping articulate a theological response to Arius, who denied the deity of Christ. Athanasius argued cogently for the deity of Christ. His short essay on the reading of old books is a minor classic itself and deserves repeated readings. Enjoy!