The Book of The Revelation draws the entire narrative of scripture to a close and explains where things are headed. The message of the book is to inform us that Jesus is coming back! It is an invitation to the reader to come TO Christ. Irenaeus, 2nd C. bishop in Lyon (France), confirmed it was written by the apostle John. Eusebius (260-339AD), in "The History of The Church" written in the second-third century, was commissioned by Emperor Constantine to document facts about the church as it was being legalized.
The Book also tells what must shortly take place (prophesy), of Jesus coming soon and setting up His Kingdom. The term "coming soon" is imagery and designed to make a dramatic impact on the reader.