The Book of Jeremiah is primarily a message of judgment on Judah for rampant idolatry. In Jeremiah 7: 30 (KJV) it is written:
For the children of Judah have done evil in my sight, saith the LORD: they have set their abominations in the house which is called by my name, to pollute it.
After the death of King Josiah, the last righteous king, the nation of Judah had almost completely abandoned God and His commandments. Jeremiah compares Judah to a prostitute (Jeremiah 2:20; 3:1-3):
20 “Long ago you broke off your yoke
and tore off your bonds;
you said, ‘I will not serve you!’
Indeed, on every high hill
and under every spreading tree
you lay down as a prostitute.
1 “If a man divorces his wife
and she leaves him and marries another man,
should he return to her again?
Would not the land be completely defiled?
But you have lived as a prostitute with many lovers—
would you now return to me?”
declares the LORD.
2 “Look up to the barren heights and see.
Is there any place where you have not been ravished?
By the roadside you sat waiting for lovers,
sat like a nomad in the desert.
You have defiled the land
with your prostitution and wickedness.
3 Therefore the showers have been withheld,
and no spring rains have fallen.
Yet you have the brazen look of a prostitute;
you refuse to blush with shame.
God had promised that He would judge idolatry most severely (Leviticus 26:31-33; Deuteronomy 28:49-68), and Jeremiah was warning Judah that God’s judgment was at hand. God had delivered Judah from destruction on countless occasions, but His mercy was at its end. Jeremiah records King Nebuchadnezzar conquering Judah and making it subject to him (Jeremiah 24:1). After further rebellion, God brought Nebuchadnezzar and the Babylonian armies back to destroy and make barren Judah and Jerusalem (Jeremiah 52). Even in this most severe judgment, God promises restoration of Judah back into the land God has given them (Jeremiah 29:10).
There is a wonderful foreshadowing in Jeremiah 23:5-6:
5 “The days are coming,” declares the LORD,
“when I will raise up for David a righteous Branch,
a King who will reign wisely
and do what is just and right in the land.
6 In his days Judah will be saved
and Israel will live in safety.
This is the name by which he will be called:
The LORD Our Righteous Savior.
These verses present a prophecy of the coming Messiah, Jesus Christ. The prophet describes Him as a Branch from the house of David (compare verse 5 with Matthew 1), the King who would reign in wisdom and righteousness (compare to Revelation 11:15). It is Christ who will finally be recognized by Israel as her true Messiah as He provides salvation for His chosen ones (compare verse 6 with Romans 11:26). Yes, you have to do a little work here on your own – flip through your Bible and look up these verses for yourself.
Jeremiah is hugely prophetical. First and foremost there is the prophecy of the Babylonian captivity of 70 years, then the prophecy of the world-wide dispersion of the Jews. There is the prophecy of the final re-gathering, the kingdom age and the Day of Judgment on the Gentile powers and the Remnant of Israel. The words prophet and prophesy occur over a hundred times in this book.