Okay the best book for a general introduction to the Mongol Empire is likely The Mongol Conquests in World History by Timothy May. After that I would recommend reading David Morgan's The Mongols. After that if your interested in looking at some more up to date stuff on the Ilkhanate I'd suggest Early Mongol Rule in Thirteenth Century Iran by George Lane. Also me and /u/Jasfss have recently participated in the Askhistorian podcasts covering Mongol rule in Persia and China.

As for the Conqueror series meh... Its generally accurate by Iggulden often embellishes, adds or adapts what we know for the sake of a better story