William McCants was able to lay out the complex history and ideology of not just ISIS, but radical Islamic terrorism in a way that people who are not well read in the topic would be able to understand it. A lot of times within the terrorism literature, that's half the battle. This is one of those books that I would classify as a solid backgrounder if you just want to know something about ISIS and a good starting point for more experienced scholars who want a quick and easy refresher on where ISIS fits within the history of Islamic terrorist groups. The one thing that always worries me with books like this is the tendency for them to be overcome by events on the ground as the months and years go by.