The Book of Omni is a very interesting one. Made more so, I think, by the fact that I used to feel it had practically no importance. It has 5 authors: Omni, Amaron, Chemish, Abinidom, and Amaleki. The plates pass from father to son except for when Amaron passes them to Chemish. These two are brothers, like when Nephi passes them to Jacob, except that these two don't have much to say.
The real meat of this chapter is written by Amaleki. He writes about Mosiah being "warned of the Lord that he should flee out of the land of Nephi, and as many as would hearken unto the voice of the Lord should also depart..." (Omni 1:12)
Mosiah and those who go with him were led by the Lord to Zarahemla and another group of people that had come from Jerusalem. These people are called "the people of Zarahemla" in the text, but the chapter heading identified them as the Mulekites. I had no idea where that information came from so I searched the internet and found an awesome article that answered a lot of my questions. It is in the March 1987 Ensign and is called
The Mulekites by Garth a Wilson. I highly recommend reading it if you want to understand the history of the Book of Mormon people. In Helaman 6:10 it tells us that, Mulek, one of the sons of King Zedekiah was brought by the Lord into the land north while Lehi was brought to the land south. The people of Zarahemla, the Mulekites, were so excited to see Mosiah and his people because they had brought with them the brass plates. The Mulekites had been brought by the Lord out of Jerusalem but had no records. Because of this, "their language had become corrupted."(v.17) Mosiah directs that they be taught in his language, the two peoples unite, and Mosiah is made king over them.
This is where the Book of Mormon history can become a little confusing. You have the Laminites in the land of Nephi in the south. The Mulekites combined with the Nephites that fled with Mosiah and both peoples together are generally referred to as Nephites. They live north of the land of Nephi. More north than that is the land where the Jaradites used to live. Coriantumr, the last the Jaradites who were brought to the land at the time of the tower of Babel, lived with the Mulekites for a time before his death and Mosiah translates engraving from a stone that is brought to him that gives an account of Coriantumr. Actually, Ether was also still alive as a witness of the destruction of the Jaradites, but the plates written by him aren't found until later.
Anyway, Amaleki writes that he has lived to see Mosiah die and his son Benjamin take the thrown. He, Amaleki, has no seed so he passes the full small plates of Nephi to King Benjamin so he can keep them with the other records. Before he does so, he writes a little about a group of people that left Zarahemla and returned to the land of Nephi. These people that left provide us with lots of Book of Mormon stories. These people are the people that fight the Lamanites off under King Zeniff who confers the kingdom to his son Noah. We then get the story of wicked King Noah, the prophet Abinadi, and Alma. We get the story of Noah's son, King Limhi and Ammon--the Mulekite, not the son of Mosiah that cuts off the arms. In fact, I have to wonder if Mosiah didn't name his son after that Ammon. Does it say that anywhere? Or was it just a common name back then? Anyway, King Mosiah, who is given the thrown by his father, King Benjamin, is the one that sends Ammon and others to find out what happened to that group of people that had left. Eventually, the Lord helps Ammon and King Limhi make it back to Zarahemla, and the Lord also helps Alma and his follows get there as well.
All very interesting stuff. I'm so glad that the Book of Omni got me thinking today.