If we were Mayans chapter 20 would be on the winter solstice 2012. This is the end - judgment day. The passage begins with one of the greatest hapaxes in all the bible. A hapax is a principle in biblical studies. It refers to a passage or concept that only appears once and its meaning is unclear. In 1 Corinthians 15 there is a passage about "baptism for the dead". A strange concept that has no explanation in 1 Corinthians 15, no support from any other book of the Bible and it is unclear just what Paul is referring to. This is a hapax. Hapaxes should be studied and pondered but held lightly and it would be unwise to build a theology around them. The concept of the millennium (our word -- Revelation simply says 1000 years) reign of Christ is quite problematic. Why would God end the world, have Christ reign and then let the evil one out again for a while? It is also important to remember, again, that John is not writing chronologically -- the events of Rev. 20 do not necessarily follow in order the things that have happened in chapter 19.
Satan's doom was decided before the foundation of the world. The great battle between good and evil is summarized in one simple sentence: fire came down from heaven and consumed them (9b). After which Satan, the false prophet and eventually death and Hades are all thrown "into the lake of fire and sulfur."
Then comes judgment day. Everyone, great and small, stand before the throne and are judged according "to their works (12)." Those whose name are not found in the "book of life" join the group in the lake of fire. It is a little unnerving to read this and be reminded that God created a moral universe. It is sobering to be reminded in this way that when it is all said and done what I did and how I lived my life will have eternal consequences. As a Christ follower I know that my name is in the "book of life." I believe I will stand face to face with my savior, the Lord Jesus Christ, and be asked to give an account of the life, talent, resources, energy, etc. that God has given me. I am occasionally driven by the thought that I have been called to make this life matter for as much as I possibly can and to make as big a difference as I humanly can. What did I do with the gifts God has given me?
This marks the end of Earth (the end of the world as we know it) and chapters 21/22 will show us the new heaven and the new earth. . .