People often think the Book of Revelation is an unimportant puzzle. Of course there are things that some people are dying to know, like "Who is The AntiChrist???" and "What does 666 really mean???" Still, most of Revelation can be summed up pretty quickly, if you are a believer…
But if you are unsure about Christianity, Revelation is a roadmap through slippery and frightening places. If you miss the early exits, coming to faith afterward will likely mean death at the hands of terrifying forces that are very opposed to Christians. If you don’t take one of those exits quickly, every other road leads to a place that is far more terrible than anything imaginable. Revelation is a merciful appeal to come to faith now, from someone that has measureless power and unquestionable authority to finally bring justice on this earth.
For those that think there’s always more time, Jesus says “I know your deeds, that you have a name that you are alive, and yet you are dead…Then if you are not alert, I will come like a thief, and you will not know at what hour I will come to you.” (Revelation 3:1-3; see also Matthew 24:36-44, 25:13, 1 Thessalonians 5:4, 2 Peter 3:10 etc.). Jesus wants us to consider the Tribulation as Imminent (Luke 12:35-48), so it's very unwise to be a part of the current world’s obviously un-Godly systems and rely on a last-minute change of heart to escape judgement.1 Let’s take a quick look.
In Chapter 1, John the Apostle writes “Blessed is the one who reads the words of this prophecy aloud, and blessed are those who hear and obey the things written in it, because the time is near!” (Revelation 1:3). There are real blessings for those who hear. Those who don’t hear should remember how fragile their life is: they never know when this world will end for them. In any case, it's not wise to throw up our hands and ignore the book entirely.
Jesus then tells John “Write, therefore, what you have seen, what is now and what will take place later”(Revelation 1:19). This tells us that Revelation can be followed somewhat chronologically.
Chapters 2 and 3 talk about the Seven Churches, which are seen as lampstands that bring light to the whole world. Not only were these real, historical churches, but modern churches and churchgoers can learn a lot from them. The key is to avoid being a part of the errors that Jesus rebukes.
Chapters 4-19 mostly concern the Tribulation. Those of us that take a “Pre-Tribulation Rapture” view of scripture understand that all of Jesus’ followers are saved from the terrible things that follow (1 Corinthians 15:52, 1 Thessalonians 4:16-18, 5:9, Revelation 4:1). Therefore, this part of Revelation is for those that come to believe (Tribulation Saints) during a future 7-year period of time.
But as we understand the character flaws of the enemies of Jesus, and see those in ourselves, then "the time is near" for us to address those flaws (see Revelation 1:3 above, also Tribulation Summoned).
Let’s pick one topic from the Tribulation, to see why it’s so important to believe Jesus now. Some think God is powerless to stop injustice and destruction, but it pains Him greatly, and He is storing up His justice that will be released when the seals are broken, the trumpets are sounded and the bowls of His wrath are poured out. At the current time (the Age of Grace), God doesn't constantly correct people for their flaws (a la lightning bolt). Instead, His justice is being stored up until the end. And though some think they will have time to get right with God, Jesus warns us that he will come suddenly (Matthew 24:27, Revelation 16:15).
Only Jesus is worthy to loose the seals of God’s justice, and those judgements fall hard on the rich (Matthew 19:23-25, James 5:1-3, Revelation 18:11-13). All through the Bible, it's easy to find scriptures that condemn the love of money (Exodus 20:17, Matthew 6:19-21, 1 Timothy 6:17-19, James 2 and 5, Revelation 18:3 etc.). Despite the warnings made so plain in the Bible, many people prostitute their morality (morals for money), just like the Great Whore, The Woman That Rides The Beast (Revelation 17:1, 19:2; see Mystery: Babylon).
As an example, let’s take the United States. People have tried to elevate themselves above God's morality since the Tower of Babel (see Genesis 11:4). The World Trade Center towers and the pentagram-shaped Pentagon have also been symbols of pride, money and power. That God allowed the terrible 9/11 attack should have been a wake up call. But instead of humility and repentance for an out-of-control economic system that enriches a very few but makes many poor, most of Christian America was prideful. America angrily accused the wrong villain, bringing many times more death and destruction to people that had no responsibility for 9/11.
Has America repented, or just swept it under the rug and doubled down? Today, serial liars are glorified from the pulpit (Isaiah 5:18-25), the love of humanity is growing cold (Matthew 24:12), the Prosperity Doctrine heresy has risen to political power (1 Timothy 6:5), greed is openly considered a virtue (Jude 1:5-11) and the earth is being destroyed (Revelation 11:18). It’s no surprise people think the Tribulation is coming soon. Covetousness (Exodus 20:17) is a common but unrecognized theme of today's world-destroying evils, and the just judgement for it is apparent in the description of the Tribulation. Many people are headed for a very rude awakening when Jesus makes them choose between habits that seem normal vs. what is truly loving (see The Number One Fundamental).
After the Tribulation, Chapter 20 describes a 1,000 year period called The Millennium. Continuing from verse 19:15, Jesus will rule with a rod of iron (see also Psalm 2:9, Revelation 2:27). The text indicates that any small injustice will be corrected. It seems this age will demonstrate humanity’s inclination to continue rebelling for no good reason, even when we are not tempted by the Devil. That is because, despite what most of us think, people are not basically good (Romans 3:10-20; Total Depravity is a foundational doctrine of most denominations). So the lesson is, there is no situation in which we do not need a Savior. At the end, our Enemy will be released briefly and another great battle will he fought. After the Devil loses again, he will be captured with a great chain and sent to the lowest hell.
Chapters 21 and 22 are among my favorite parts of the Bible. Everyone sheds tears at some time in their life, but here, all the tears are wiped away. Everything that offends is kept outside the gates of a very large city (New Jerusalem, about half the size of the United States, but extending far into the heavens as well) where gold is used for pavement. Nothing bad happens after this, ever. I expect to be finally at peace there, living in a better world with all the animals (Revelation 5:13) in my own mansion (John 14:2). It will be better than the Garden of Eden, and I will be enjoying the good times with my friend Jesus. I sure hope to see you there too.
 Many Christians hold to a Pre-Tribulation Rapture (Pre-Trib). Any Christians alive just before the Tribulation are brought up to heaven suddenly, in the Greek harpazo (1 Thessalonians 4:17). Scripture is unclear when this will happen though, so it is more important to believe in the doctrine of Imminence. Many people seem to think Jesus will give them a break at the last minute, but the Bible says there will be no time for that. If some reject Imminence because it sounds like fear-mongering, remember Proverbs 1:7. There is good reason to be ready (Zephaniah 1:14).
 See Job 1:10-17 to understand how evil is restrained by God, and how God allows the wicked to correct His people. The World Trade Center and it's military mistress, the Pentagon, were attacked on 9/11. To demonstrate the connection between money and miltary power in America, see War is a Racket, General Smedly Butler.