Is there one main theme that unites all the books of the New Testament?

The main theme of the whole Bible is God's sovereignty, which was rejected by Adam and Eve. Read Genesis chapter 3, which is mankind's history, with its consequence to this day. Read Romans 5: 12.

Matthew 6: 9,10 shows that Jesus told us to pray for God's kingdom to come, where His will, will take place as in heaven also on earth. God's kingdom is the government that will undo all the harm that millenniums of human rule have done. It will provide: perfect health, peace and security, and a clean environment for all those who choose God's sovereignty.

Psalm 37: 29 reads: " The righteous will possess the earth and they will live forever on it.

The Bible is a library of 66 Books. The New Testament begins with the genealogy of Jesus Christ and his preaching activity about God's kingdom to come.

1 John 5: 19 reads: " The whole world is lying in the power of the wicked one. Revelation 12: 9 reminds us that the wicked one is " The original serpent, the one called Devil and Satan, who is misleading the entire inhabited earth. The original serpent in found in Genesis 3: 5 where he promised Eve that she will be like God. Well ! that did not happen, did it?

The only way to be able to live and benefit from God's sovereighty is to be no longer under Satan's influence. The Bible is the inspired letter from God according to 2 Timothy 3: 16,17 and beneficial for us to become fully competent completely equipped for every good work. It is the way that God has chosen to communicate with mankind.

Matthew 4: 4 reads: " Man must live, not on bread alone, but on every Word that comes from Jehovah's mouth". And Jeremiah 10: 23 reads: "It does not belong to man who is walking even to direct his step."

So to understand our past, present and future we need the whole Bible of 66 books.