Okay, I'm going to be perfectly honest. I only read Cowboys and Aliens because I like Daniel Craig and I wanted to know more about the movie. If you have no idea about the movie then you can watch the trailer. After watching the trailer and reading the graphic novel I think the movie diverges away from some of the story.
The basic premise is that in 1870s Arizona (think Wild West), aliens crash land and try to take over the primitive life as slaves. Intriguing premise, great opening pages from the view point of both the White Men and the Aliens as conquerors. Then the actual story begins: Zeke and Verity are protectors of a wagon train leading them through the treacherous wilderness to their new life in Silver City. When Zeke goes for reinforcements at the fort, an alien ship crash lands nearby. Once the aliens disembark they begin systematically destroying those that challenge them. Only partnering with the local Apache tribe and using human ingenuity can save them.
And let's be honest, who wouldn't love to see if human ingenuity would beat out superior technological weapons?