If I had only one...
Imitation of Christ: For five hundred years, this gentle book, filled with the spirit of the love of God, has brought understanding and comfort to millions of readers in over fifty languages, and provided them with a source of heart-felt personal prayer. These meditations on the life and teachings of Jesus, written in times even more troubled and dangerous than our own, have become second only to the Bible as a guide and inspiration. The Imitation of Christ was written in Latin by Thomas Hemerken of Kempen, or Thomas á Kempis as he is now known. It is essentially a spiritual diary. Thomas, born about the year 1380, was educated by the Brethren of the Common Life, was moved to join their community.
Quote: "When the day of judgment comes, we shall not be ask what we have read but what we have done, not if we have made fine speeches or debates but if we have lived faithful lives."
A couple different editions of this work are floating around on the market, you can find a good Bible centered translation with footnotes listing all the Biblical quotes.