Water from an Ancient Well by Kenneth McIntosh is one of the most quietly wise books I've read in a long time. "Like a Celtic knot, this book is meant to be enjoyed in a nonlinear fashion," McIntosh states in his introduction. Each chapter is a self-contained essay on a particular topic in Celtic Christian spirituality, with stories, theological-historical background, and applications for today. A lot of my favorites are here: St. Brigid of Kildare, the Gaelic hymn "Be Thou My Vision," the Celtic sunwheel cross, St. Columba, St. Brendan the Voyager, even Merlin the Magician. Quotes from C. S. Lewis, "the great Celtic theologian of modern times," are peppered throughout the book. My favorite chapters are the ones about the panentheism of John Scotus Erigena ("Every Bush Aflame: God Revealed in Nature") and the one about "Furred and Feathered Neighbors: Creatures of Grace," which shows how St. Columba, St. Brigid, and others related to their animal neighbors. If you're not familiar with Celtic Christian spirituality, Water from an Ancient Well is a great introduction. Even if you are familiar, this book is a great way to revisit some of these stories, poems, and prayers and learn new ones.