A reference request for a book on: "What Happened to the Seven Churches of Revelation?"
The content of the book discusses the messages to each of the churches as written in Revelation and how to interpret each of those messages. But the book also discusses what happened to each of the churches after they received the letter (for example, the Church of Laodicea took the warnings to heart, revived, and lasted until the 1500s).
Can not confirm absolutely, but it may be that your memory may be a little vague here. For example, you believe the book mentions that the Church of Laodicea took the warnings to heart, revived, and lasted until the 1500s.
Ongoing excavations of the city of Laodicea began only recently, in 2003. The work continues to uncover an expansive, wealthy city. Laodicea was built on a major highway and became a commercial and banking center. It was known for ear and eye medicine and for its black wool. The water was tepid and unpleasant, but nearby Hierapolis gushed hot thermal springs. Also nearby, Colossae was the home of pure, cold water.
The churches in Hierapolis, Colossae, and Laodicea were relatively close and seemed to have a relationship with one other. Paul instructed that his letter to the Colossians be read also in Laodicea (Col. 4:16), and he was encouraged by their strong faith in Christ (Col. 2:5). Something seems to have changed, however, in the thirty years after Paul’s letter when John penned the book of Revelation. Wealth and independence had weakened their commitment to Christ.
In Revelation 3, Jesus used language and imagery familiar to them: riches, eye medicine, white clothing, and tepid water. He said, “I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! So, because you are lukewarm—neither hot nor cold—I am about to spit you out of my mouth. You say, ‘I am rich; I have acquired wealth and do not need a thing.’ But you do not realize that you are wretched, pitiful, poor, blind and naked” (Rev. 3:15–17 NIV).
Most citizens of Laodicea resettled into the modern-day city of Denizli after a devastating earthquake in 600 AD. It seems the ancient city fully died out after the Turks came through in the eleventh century. Today Denizli is a bustling city of over half a million. Out of that number, three or four former Muslims have stepped out to profess faith in Christ.
Sardis, however, archeologically has shown evidence that they did indeed repent from their evil ways. There are no Christian there now. But there is evidence that a Byzantine Church was built there about a hundred years after St. John’s death.
Jesus’s words in Revelation sliced through Sardis’s thriving “health” to the church’s spiritual realities. Although there were a faithful few, most people in the Sardis church were spiritually dead and dying. Christ summoned them to “wake up,” “remember,” and “repent” (Rev. 3:2–3 NIV). Ruins from a small, fourth-century Byzantine church stand on the grounds of the Temple of Artemis. I found the crumbling church—built a few hundred years after John’s letter—to be a hopeful sign that some in Sardis took the warning to repent.
Just a little map to indicate the region we are dealing with.
Map of Western Anatolia showing the "Seven Churches of Asia" and the Greek island of Patmos.
In the end I suspect that one of these books is the one that you are looking for: