In this, Genghis continues to kick the shit out of any nation that so much as looks at him funny, while still finding time to be a dick to his kids. He also meets a new enemy that might just be as formidable as he is, while also realising that simply leaving a place once you've annihilated it doesn't mean it stays annihilated, and that he might just have to fight them again on his next trip through. Sadly, there's no time for a second beating before karma stabs him right in the gut. It couldn't have happened to a nicer bloke.
I see now that this isn't actually a trilogy and that the story continues - this time presumably with Genghis' grandson, Kublai, in the lead. I'm not going to be rushing out to read it, as I imagine that it's just more of the same, only with Genghis' name tippexed out and Kublai's name scribbled in the margin.