In a word, unputdownable! (If it is not a word then it should be.)
These books are excellent. Vivid, intriguing, exciting, at times horrifically violent, they take you on a journey alongside one of history's most daring, ruthlessly efficient leaders. They show you the whole man, not just the infamous character he became historically. Iggulden's knowledge is superb and the picture he paints of Genghis Kahn's life and surroundings is sharp, clear and vibrant. I read these books over two years ago now and I still think about them and talk about them to other keen readers, and I have recommended them by word of mouth on numerous occasions.
This reminds me of a real life Game of Thrones, minus the magic and mythical creatures. In fact I often wonder if GoT borrowed certain real events because some of the things that actually happened to or because of Genghis Kahn - and certainly particular punishments and rulings he dished out - are mirrored in that series. No matter, I just think it is an interesting parallel and am not suggesting for a minute that there is anything wrong with it.
If you like your history with more than a dash of excitement and a little violence does not put you off, then I whole-heartedly recommend this series. These are among some of my favourite books to grace my shelves and I have no doubt that I will one day return to them and read them all over again. Excellent!