There are numerous keys that unlock our understanding of the book of Revelation. But there are two chapters within the book itself that bring the whole book in proper perspective. Those two chapters are 13 and 17. These two chapters are related to each other. Both reveal the timeframe that Revelation deals with. Both deal with the seventh kingdom (world empire) of the world – which is the one we’re living in now as the Church age. While chapter 13 deals with the whole extent and nature of this kingdom, chapter 17 deals only with the end of this kingdom when the “eighth king” rises to power just prior to the return of Christ. This awareness brings this whole book together. It makes interpretation of the events of this much easier to identify.
Therefore, I suggest to everyone who wants to understand this book, start with these two chapters. Below are links to my commentary on these chapters. I think you’ll find that they make a lot of sense.