As a priest writer and with a pontifical Doctorate in Church History – who also once managed a Catholic book store a few blocks away from the White House – I am frequently asked what books are simply indispensable for a serious Catholic to have always close at hand, whether in hard copies on the bookshelf or nightstand (some of us still remember books with spines made of real paper), or more commonly now on Kindles or iPads.
I reply simply: 1) the best version you can find of the New Testament, and 2) almost as important, the latest version of The Catechism of the Catholic Church  – this later being arguably the greatest product of the Second Vatican Council. Although it was very long in coming (St. John Paul II promulgated it in 1992, which is to say twenty-seven years after the close of the Council), it was well worth the wait.
The result is that now, any serious Catholic can simply look up, in print or online , the answers they need to crucial questions. The Catechism is indispensable for one’s own knowledge and practice and growth in the Faith. But it is equally important to enable us to do what should come naturally, i.e., to share our joyful Faith with the many thousands of people with whom we will come in contact over the course of a whole lifetime.
After all, do you want to face the Lord at your particular judgment with empty hands when he asks, “how many souls did you bring to me or how many did you bring back to me? Ask yourself seriously: How will I respond? Where you will wind up in next life may depend upon your zeal and generosity in sharing Jesus and His Church with others, when you had the opportunity to do so.
Given the challenges involved in that task in our day, there are other things we need. A neglected dimension of the crucial knowledge every Catholic should have is deep immersion in Church History. George Santayana, the American philosopher, famously remarked that those who ignore the past are doomed to repeat it. This is an especially important warning for us in the United States.
The widespread ignorance of U.S. history is both a national scandal and a sad joke, particularly given the relatively short time of America’s existence in comparison to so many other countries throughout the world. Knowing our own past helps give direction and meaning to our present and guides us into the future.
This is even more true when it comes to the millennia-long history of the Catholic Church with its deep roots in the history of Israel, through the birth, death, and Resurrection of Our Savior, Jesus Christ, the growth and travails of the Faith over the centuries, which will only cease at the end of time and the Last Judgment.
What other history is so varied and exciting? Catholicism boasts: victories and defeats, saints and sinners, founders and Fathers. We have warriors, peacemakers, monks, martyrs, heretics, hermits, virgins, mystics, scientists, and apparitions. Catholics have created great religious painting and sculpture, and magnificent cathedrals. In music there art soaring liturgical composition, chants, and hymns. In poetry and literature, we have given the world Dante, Chaucer, Shakespeare, Chesterton, Belloc, Waugh, Knox, Bernanos, Mauriac, Gilson, and Maritain. And we have the beauty of the Latin Mass
And now we’re in the wonderful position of having effective means of bringing the history of the Faith to the whole world via Vatican Radio, EWTN, and the Internet. But to stick with books for a moment, just a few further suggestions the Church’s history and teaching:
1. Every Catholic school in the country, without exception and at whatever level (including colleges and universities), should have mandatory and appropriate courses in the history of the Catholic Church.2. For adults, I have many favorites, beginning with anything by the late Warren Carroll of Christendom College, who is the best Catholic Church historian of our time.3. And I encourage reading anything by Diane Moczar, especially What Every Catholic Wants to Know . Also, take look at The Ancient City  by Numa Denis Fustel De Coulanges to understand how the introduction of Christianity into the ancient world changed everything. And we now have a simple, clear, and recent History of the Church  by the American historian James Hitchcock – a good starter for the beginner.
As for spiritual reading, the field is vast and incredibly rich. Let me just suggest that you look up my Catholic Lifetime Reading Plan . I have about 100 titles there and constantly add and update as seems appropriate, so that you may easily find classic works as well recent texts that help guide you through the many mansions of our long tradition.