It's a little weird to jump from Joshua, where the people pledge allegiance to God and promise to serve him and him alone, to 1 Kings and the political intrigue between King David's brothers. There's plenty of politics in our world, but generally speaking political leaders in the United States don't kill each other. At least I don't think so.
Long story short, once Joshua died, the people turned their backs on God despite their promises to serve him.
See, they followed God by following Joshua. And once Joshua was gone, they didn't know how to follow God on their own.
Eventually, they begged God for a king, so they could be like other nations, so they could have a leader to follow. And God gave them what they wanted--with a stern warning. (You can check it out in 1 Samuel 8:4-21.)
The thing was, not all the kings followed the one true God, and whenever the king walked away from God, the people suffered.
1 Kings tells the story of the Kingdom of Israel after the death of David, the lure of idols, and God's love and compassion.
Of note, books like 1 Kings remind me to keep my eyes on God and not on man. I have tremendous spiritual leaders in my life, but none of them are perfect.
You can get some background about the book of 1 Kings at this link: