"The Mysteries of Christianity", Fr. Mathias Joseph Scheeben. People here may be familiar with his work: "The Glories of Divine Grace"; this work takes one through the deepest questions of Catholic doctrine: The Blessed Trinity; the Incarnation; Original Sin; the Redemption; etc. etc. Its not written in the style of a manual of dogmatic theology; it is written in essay form, drawing from both the Scolastic sources and Patristic; he enthralls the reader with his beautiful descriptions of the mysteries of our faith. I highly recommend this book; its well worth the effort.