In this chapter, Israel is defeated by the Assyrians several times and several kings are assassinated by their own men.
This chapter continues with Israel traveling down their grim road towards destruction and Judah slowly following. Through all of Israel's history, it has been plagued by instability with numerous violent coups overthrowing one king or another. It has had brief moments of continuity, like in the brief dynasty under Ahab and now Jehu, but things really seem to be getting unhinged here towards the end. Several kings die in quick succession (note how short some of these kings are reigning; Zechariah reigns for six months, Shallum for only one month and Pekahiah for two years). When Menahem takes power (by killing his predecessor), he goes even further by sacking one of the towns of Israel and killing its pregnant women (we can assume men and children likewise died). This is remarkable brutality directed towards his own people.
For Israel, we really are getting to the end of their independent sovereignty. In this chapter, they are crushed not once but twice by the Assyrians, first paying the Assyrians off with 37 tons of silver and then second losing a large swathe of territory along with however many people were killed or deported.
There are a lot of things happening in this chapter that we don't exactly see, but can figure out if we start reading between the lines. The first I will mention is that Israel appears to form an alliance with Aram. This is a bit surprising because it was not too long ago that Israel was allied with Judah in their war against Aram, and now they are allied with Aram in their war against Judah. It's a remarkable turn of events, likely driven by the pressure coming against both Aram and Israel from the Assyrians. The effects of this alliance are fairly obvious: Judah is now under even more military pressure from this northern alliance as well as the larger threat of the Assyrians. For Israel, this relieves some of the pressure off of them, but it opens them to a greater risk of falling under God's judgment because they are now allied to an idolatrous nation.
Another thing happening in this chapter is the moral decline of Judah's kings. Similar to the story about Amaziah (see 2 Kings 14:19), Azariah starts off as a fairly good king, but has a bad ending. In verse 3, it says that Azariah does good things just like his father, in verse 4 it tells us that he nevertheless committed the same sins as his father, and in verse 5 it tells us that he was afflicted with leprosy until death. What it doesn't tell us (but we know from the book of Chronicles), is that the leprosy was a punishment from God because Azariah commits a particular sin which we will read about then. This is very similar to Amaziah who also sins towards the end of his life and is assassinated as a result. We don't see any negative behavior from Jotham (the last king of Judah in this chapter), but both Amaziah and Azariah fall into sin towards the end of their lives and neither one dies in peace.
I have a few more comments about names in this chapter. First, we see a "Pul" and "Tiglath-Pileser" in verses 19 and 29 respectively. In fact, these are two names for the same king of Assyria. Second, this chapter also refers to "Jotham son of Uzziah" and "Jotham son of Azariah". This is because Uzziah and Azariah are two names for the same king of Israel. It's confusing, but that's just how things go in the OT.
I don't have much else to add about this chapter. We see several more kings of Israel get assassinated and replaced by their murderer. These kings continue to do "evil in the sight of the LORD", and Israel continues to be punished by God for breaking the covenant. The overall theme of this chapter matches very closely with the themes of Kings as a whole: Israel is in the midst of violent upheaval, pressure from without and idolatry and coups from within, and Judah started off in better condition but is progressively drifting towards the same idolatry that is afflicting Israel and is at risk of the same judgment from God. Things will need to change soon for both Israel and Judah if they are to avert their fate.