Seven Letters As A Literary Unit

The seven letters to the seven churches make up a single piece of literature, in connection with the first chapter of Revelation. In the first chapter is the basic description of the glorified, powerful Jesus, which the seven letters refer to throughout.

The seven letters themselves make a chaistic pattern, where the first letter is connected to the last, the second letter connected to the second to last, and so on. The chaistic pattern can be seen as following:

Ephesus-- Condemned
Smyrna—Approved
Pergamum—Some condemned, some approved
Thyatira—Some condemned, some approved
Sardis—Some condemned, some approved
Philadelphia—Approved
Laodikia-- Condemned

Thus, Revelation 1:10 through the end of chapter 3 make a separate literary unit and can be read as such. However, they also fit within the larger pattern of Revelation as a whole, as these letters throw many hints of the troubles and judgments to come.

In a sense, these seven letters are the heart of the Book of Revelation, the action that is required due to the coming judgment to come. It is encouragement to stay strong in the mist of persecution, to resist the corruption of the world, so the church does not end up on the wrong side of the judgment in the eschaton to come.