I think the meaning for the book as a whole is that good doesn't always win, there isn't always a happy ending. People who have committed crimes don't always get caught. However, the bad people who commit those crimes aren't always without morals. Chigurh for example has personal morals that he doesn't break throughout the book. He makes a promise to someone he won't ever break it, including the one he made to Moss about killing Carla Jean. But the interesting thing is that he gives the money back. He doesn't keep it for himself which points the reader into thinking that while his moral compass is seriously skewed he sticks to what he thinks is the right choice.
In the end of the book, I don't think there is any unfinished business. Chigurh pretty much killed everyone who had an idea of who he was. Then sheriff Bell retiring seemed appropriate, he felt is whole life was a lie and I think this case really pointed that out to him. It showed him what really matters in his life, his wife, and he doesn't want the only real thing in his life to be killed by Chigurh who seems to him to not have a problem with killing anyone. Moss dying was inevitable, some unknown welder takes some drug cartel money was not going to end well. I think they only mystery was who was going to kill him and who else would die because of his choice.
I feel like the manhunt in the novel was not the first one for Chigurh and it sure won't be the last one because I think Chigurh lives on the thrill of it.