Despite the fact the book has a great deal to say about coming events, Revelation is not a roadmap of the future. It is, rather, an exhortation for today. It is possible that people living in the tribulation will pick up the book of Revelation and see the things spoken of being fulfilled in their lives, but the people living at that time will be under a delusion (2 Thess. 2:11). It is unlikely that those under the judgment of God will have the spiritual insight to believe what the book teaches (see Rev 6:12-17). Revelation was intended to be read by the church living in the shadow of the Second Coming bearing up under persecution for their belief in Jesus, in order to encourage them to be strong and endure until the end. As such, the book is an excellent conclusion to the Jewish-Christian literature in the NT.
I am convinced that the main theme of Revelation is worship. The fact that God is worthy of our worship appears many times in the book. There are several scenes of heavenly worship around the throne of God (Rev 5:13, 7:11-12). The reason for God’s worthiness is that he is the creator (Rev 4:11) It is evident that since God is the creator of all things, he is sovereign over them and can use them in what ever way he chooses. In Rev 10:6 the elements of nature that God is declared to be creator of are the elements of creation that are used to judge in the book.
God is also described as a just judge who will avenge the wrongs done to his people. Even this can be seen as a sub-theme of worship. Rev 16:5, for example, describes an angel worshiping God as the one who is “just in all his judgments.” In Rev 18:20, the saints are to rejoice because God has judged the Great Whore of Babylon.
Bibliography: M. Eugene Boring,“The Theology of Revelation, ‘The Lord Our God the Almighty Reigns,’” Interpretation 40 (July 1986), 261.