Bones of the Hills, by Conn Iggulden. I give it a four-and-a-half.
It tells a story of the Mongol Empire under the rule of Genghis Khan, and how he invaded Aarab and Asian lands. Of course there's no way a 500+ page book can accurately tell a story set in year 1100-1200, so it is kind of half fiction, half fact. But it's a great read.
It explains in great detail how Mongol boys were taught to ride, shoot a bow, wield a sword, wrestle, and endure excruciating pain as soon as they could walk. It gives a sense that they were great and honourable men, and hides the more offending sides that have been discovered to the (then)Mongol Empire. And even though you know it's not all true, it's just too awesome not to be drawn in completely.
I revolves around Genghis, his generals, and his family, and all of their doings. Mostly set in what is now Iran and Iraq, you also grow fond of the characters and their unique traits. I found myself quite pissed when my favourite character didn't end up being the heir of the Empire. And later died.
I highly recommend it to everyone.