Check out this video documentary series from Vice News. Medyan Dairieh, a reporter with Vice, spent 3 weeks imbedded with The Islamic State. The series follows Dairieh as he reports from within IS headquarters in Syria and then documents IS as they invade and occupy Iraq.
Although it is clear that IS had a heavy hand on what they allowed to be filmed (or not filmed), the series offers a unique look into the inner workings of the extremist group and is definitely worth the watch.
Part 1 of the video series can be viewed here.