OF ALL THINGS CATHOLIC, there is nothing so familiar as the Mass. With its timeless prayers, hymns, and gestures, the Mass is like home to us. Yet most Catholics will go a lifetime without seeing beyond the surface of memorized prayers. Few will glimpse the powerful supernatural drama they enter into every Sunday. Pope John Paul II has called the Mass “heaven on earth,” explaining that “the liturgy we celebrate on earth is a mysterious participation in the heavenly liturgy.”

The Mass is near and dear. The Book of Revelation, on the other hand, seems remote and puzzling. Page after page flashes bizarre and frightening images: of wars and plagues, beasts and angels, rivers of blood, demonic frogs, and seven-headed dragons. And the most sympathetic character is a seven-horned, seven-eyed lamb. “If that’s just the surface,” some Catholics say, “I don’t think I want to see the depths.”

Well, in this little book, I’d like to propose something outlandish. I propose that the key to understanding the Mass is the biblical Book of Revelation—and, further, that the Mass is the only way a Christian can truly make sense of the Book of Revelation.

If you’re skeptical, you should know that you’re not alone. When I told a friend that I was writing about the Mass as a key to the Book of Revelation, she laughed and said, “Revelation? Isn’t that just weird stuff?”

It does seem weird to Catholics, because, for many years, we have been reading the book apart from Christian tradition. The interpretations most people know today are the ones that have made the news or the best-seller charts, and those have been overwhelmingly Protestant. I know this from my own experience. I’ve been studying the Book of Revelation for more than twenty years. Until 1985 I studied it as a Protestant minister, and, down through those years, I found myself engaged, in turn, by most of the fashionable and unfashionable interpretive theories. I tried every key, but none could open the door. Every now and then, I heard a tumbler click, and that gave me hope. Yet only when I began to contemplate the Mass did I feel the door begin to give way, a little bit at a time. Gradually, I found myself taken up by the great Christian tradition, and in 1986 I was received into full communion with the Catholic Church. After that, in my study of the Book of Revelation, matters became clearer. “After this I looked, and lo, in heaven an open door!” (Rev 4:1). And the door opened onto… Sunday Mass in your parish church.

Now, you may reply that your weekly experience of Mass is anything but heavenly. In fact, it’s an uncomfortable hour, punctuated by babies screaming, bland hymns sung off-key, meandering, pointless homilies, and neighbors dressed as if they were going to a ball game, the beach, or a picnic.

Yet I insist that we do go to heaven when we go to Mass, and this is true of every Mass we attend, regardless of the quality of the music or the fervor of the preaching. This is not a matter of learning to “look at the bright side” of sloppy liturgies. This is not about developing a more charitable attitude toward tone-deaf cantors. This is all about something that’s objectively true, something as real as the heart that beats within you. The Mass—and I mean every single Mass—is heaven on earth.

I assure you that this is not my idea; it is the Church’s. Neither is it a new idea; it’s been around since the day John had his apocalyptic vision. Yet it’s an idea that hasn’t caught on with Catholics in recent centuries—and I can’t figure out why. Most of us will admit that we want to “get more” out of the Mass. Well, we can’t get any more than heaven itself.

I should say from the start that this book is not a “Bible study.” It is focused on the practical application of just one aspect of the Book of Revelation, and our study is far from exhaustive. Scholars debate endlessly about who wrote the Book of Revelation, and when, and where, and why, and on what sort of parchment. In this book, I will not take up these questions in any great detail. Neither have I written a handbook on the rubrics of the liturgy. Revelation is a mystical book, not a training video or a how-to manual.

Throughout this book, you will probably encounter the Mass in new ways—ways other than the one you’re used to attending. Though heaven touches down whenever the Church celebrates the Eucharist, the Mass looks different from place to place and time to time. Where I live, most Catholics are accustomed to the liturgy of the Latin Rite. (In fact, the word “Mass” properly refers only to the Eucharistic liturgy of the Latin Rite.) But there are many Eucharistic liturgies in the Catholic Church: the Ambrosian, Armenian, Byzantine, Chaldean, Coptic, Malabar, Malankar, Maronite, Melkite, and Ruthenian, among others. Each has its own beauty; each has its own wisdom; each shows us a different corner of heaven on earth.

Researching The Lamb’s Supper has given me new eyes to see the Mass. I pray that reading this book gives the same gift to you. Together, let’s ask for a new heart as well, so that, through our study and prayer, we may grow more and more to love the Christian mysteries that we have from the Father.

The Book of Revelation will show us the Mass as heaven on earth. Now, let’s press on, without delay, because heaven can’t wait.