Vice is running a series of reports from inside ISIS, the so-called Caliphate that has taken over eastern Syria and parts of western Iraq.
Below was the first installment; others are available at their web site here.
The "speed" at which ISIS took over western Iraq is simply a function of the power vacuum there, and the utter disarray and incompetence of the Iran-backed government, which is responsible for much of country's chaos and despair.
This is a highly sanitized version of what a regular person experiences; there are plenty of outright lies (treatment of the Christians) as well as omissions. Still, though the reporting was done under heavy supervision/censorship, the reporting crew displayed singular courage in putting this together.
Besides the gruesome sights, the most chilling thing are the kids.