Revelation is considered a very complicated book because it's prophetic. It doesn't tell a story that has already happened and it isn't offering advice--instead, it discusses what will happen in the future, near the end of the world. I'm going to go ahead and use some Google-search images to help illustrate Revelation, because the visual elements are really hard to fathom otherwise.
John has been exiled to the island of Patmos, and while he is there, God gives him a revelation or a prophetic vision of the end of the world. The point of all this end-times prophecy is to show that the world is not permanent. And end will come, and Jesus will return. Those who love him will be saved, and those who don't will be cast out. God emphasizes his power when he begins speaking to John in 1:8-- "I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty."
God gives John a message to preach to the the 7 main churches of Christianity, and I think the seven churches represented were actual locations of churches at the time (Ephesus, Smyrna, Pergamos, Thyatira, Sardis, Philadelphia and Laodicea), but that they also in some way apply to the different bodies of believers in different places in the future. John sees a vision of 7 candlesticks which represent the churches, and Jesus is walking among the candlesticks. God has a special message for each of the churches, some involving praise and some involving a stern warning.
Chapter 4 shows the throne of God in heaven, and proceeds to depict the judgements God delivers upon the earth in the final days. It's worth noting that in heaven everyone, whether angel or human, is always worshipping God and giving honor to him, saying things like: "Thou art worthy, O Lord, to receive glory and honour and power: for thou hast created all things, and for thy pleasure they are and were created." (4:11).
Chapter 5 begins the judgements of the Seven Seals (wax seals which keep a book closed). As each seal on the book is opened, a new plague is unleashed on Earth because of the sinfulness of Earth's residents. Among the seals are the Four Horsemen of the Apocalypse, spirits that ride on horses and cause famine, war, pestilence, and death.
After the Seven Seal judgments, there are the Seven Trumpet judgments in Chapter 8, which are even worse. Among all these punishments, the Antichrist (the Beast) rises and gains power over all the people that remain in the world. John also discusses how God will protect the nation of Israel in the final days. Chapter 16 brings the final Seven Vial judgements. Chapter 20 brings the final judgment on Satan, who is thrown into the lake of fire which has been prepared for him.
In Chapter 21, God makes all things new. "And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God. And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away." (21:3-4) So after all this devastation, and even after the end of the world itself, God's love toward humanity is still in evidence.
Revelation, in short form: Evil is destroyed, Jesus wins, and if you love Jesus, you win also.