In this chapter, Manasseh becomes king, leads Judah into idolatry but then repents of his mistakes.
This is the second time we get to read the story of Manasseh's life. Similar to the other kings, Manasseh was previously described in the book of Kings (2 Kings 21, to be particular). Most kings are described similarly between Kings and Chronicles. However, in the case of Manasseh, there are substantial differences which I will describe below.
This chapter has three main sections. The first section is verses 1-9, which describe Manasseh's intent to do evil, leading Judah into idolatry. This section is substantially equivalent with the passage in 2 Kings. Besides listing the things that Manasseh was doing wrong, it also compares his actions against God's word, quoting (or sometimes paraphrasing) things the LORD said earlier. Basically what this is doing is juxtaposing Manasseh's actions against God's standard, and showing all of the ways that the king is falling short. Both verse 4 and verse 7 emphasize that Manasseh is performing idolatry in the very temple that God said would keep his name forever. Verse 8 says that Israel (and Judah) would remain planted in the promised land forever, so long as they obey the LORD's commands. This chapter is documenting their sins and violations of the LORD's commands to establish the context for their eventual removal from the land.
The second section is verses 10-20, which describe God's response to Manasseh's sins. It begins in verse 10 with a prophet's rebuke, but when the king and the people do not listen to the prophet, God's judgment swiftly follows.
This whole section is almost completely absent from 2 Kings 21, and it constitutes the largest difference between how these two books describe the life of Manasseh. In fact, the comparable section is 2 Kings 21:10-18, which besides giving us a detailed prophecy about the destruction of Jerusalem, lists even more sins committed by Manasseh in addition to what he did wrong in the previous section. It is obvious when reading 2 Kings that the tone used to describe the life of Manasseh is overwhelmingly negative. In the larger context of Kings, Manasseh is (perhaps surprisingly) the main person blamed for the Babylonian exile (see 2 Kings 24:3-4).
The narrative in Chronicles is much more nuanced. In Chronicles, Manasseh is not directly blamed for the exile, and when Manasseh is punished by God and taken into exile by the Assyrians, he repents and is restored by God. The rest of his life is comparatively positive, removing all the idols and bringing the people back to God. Although Manasseh's initial sins are still firmly condemned by the Chronicler, Chronicles presents his life as much more of an arc, going at first into dark, evil behavior, but finding humility in the midst of God's punishment and being restored into his position as king at the same time that his faith is rebuilt.
The third and final section is verses 21-25, which describes the reign of king Amon. This section is also very similar to the corresponding passage in 2 Kings. It describes Amon as an evil man who is killed by his own servants. The only major difference is that verse 23 in Chronicles contrasts the repentance of Manasseh with the unrepentant evil of Amon. The comparable passage in Kings is 2 Kings 21:20-21, which basically says that Amon walked in exactly the same evil ways as his father Manasseh.
It's quite a contrast. If we only had the book of Kings, we would have never suspected that Manasseh might have repented of his sins and tried to lead Judah back to the LORD. There are two questions I would like to address. First, why do I think Kings and Chronicles wanted to represent such contrasting stories about the life of Manasseh when (presumably) they both had the same source material describing his reign? Second, just looking at the book of Chronicles, what lessons can we learn from Manasseh's life story?
To answer the first question, I cannot offer much more than speculation. We are basically trying to understand the author's motivation, and that can be notoriously difficult under even the best of circumstances. That said, I will now begin wildly speculating. :) I think the largest difference between these books is the context in which they were written and finalized. Kings was largely finalized as a mid-exilic book. That is, it was substantially compiled and edited during the Babylonian exile, though much of the source material would have been pre-exilic. During the exile to Babylon, the Jewish people were faced with many existential questions*, one of the foremost being, "how could this have happened?" I believe that Kings in general, and 2 Kings 21 in particular, is one attempt at answering that question. It construes a deeply negative attitude towards Manasseh because it is trying to figure out what could have gone wrong that this terrible judgment from God could have fallen upon Judah. Kings finds a large part of its answer in the idolatry and sins of Manasseh, though many of the kings who follow him are also regarded as evil, sinful men, and it's all written in the larger context of the Kings moral narrative (which is beyond the scope of my comments here).
On the other hand, Chronicles was edited and finalized as a post-exilic book. That is, it was substantially compiled after the return from the Babylonian exile, though it too derives much of its content from pre-exilic sources. After the Babylonian exile, one of the foremost questions asked by Jewish society was, "how do we restore our cultural identity?" The book of Chronicles attempts to answer that question by focusing an enormous amount of time and energy on the temple worship system and the Davidic dynasty. Chronicles attempts to draw the people back to a better, idealized time when David and Solomon reigned, to serve as a model for how they should rebuild their society in the "present day" (i.e. ~530 BCE).
"How could this have happened" is no longer a core, existential question because while the Babylonian exile was a deeply traumatic event, it was tempered by the subsequent return to the promised land during the reign of Cyrus. Although it is hard to draw broad generalizations, I think that Kings is more persistently negative because it was written in the midst of that national trauma, while Chronicles is more generally positive because it was written in the midst of the hopeful restoration period.
Both Kings and Chronicles are looking back, but they are looking back for different reasons. Kings is looking back to find what went wrong, and Chronicles is looking back to find a vision of society that they should strive for. Neither of them is unbiased exactly, so I don't think we should look to one or the other to try to find an "objective" account of Manasseh's life.
For the second question (what can we learn from Manasseh's life), I think the description of his life is strongly representative of the sin/judgment/repentence/restoration paradigm that is presented in various places throughout the OT. I would like to specifically reference 2 Chronicles 7 since that chapter sets the tone for so much of the rest of Chronicles. Besides foretelling the exile, 2 Chronicles 7:13-14 also establishes the sin/judgment/repentance/restoration pattern, though at a national level rather than an individual level. Nonetheless, Chronicles makes it clear that even in the midst of judgment, if the people repent then God will bring restoration and healing, and we see that in Manasseh's life. Therefore I believe that Chronicles is seeking to portray Manasseh as an individual example of the biblical pattern laid out in 2 Chron 7.
Furthermore, we can also see shadows of Judah's history in the life of Manasseh. Judah herself committed many sins, was taken into exile to Babylon (like Manasseh himself, v. 11), repented and was restored to the promised land. That mirrors almost exactly the life of Manasseh as it is described in Chronicles.
In conclusion, I think the life of Manasseh is closely aligned with the overall message of Chronicles, emphasizing God's judgment that follows sin and his restorative acts that follow repentance. The life of Manasseh is a microcosm of Judah's story and complicated relationship with God.
In the next chapter, Josiah becomes king and ushers in the final revival in the book of Chronicles.
*Other questions, such as "how do we sustain our faith in a hostile and idolatrous society?" are the subject matter for other books like e.g. the book of Daniel.