One of the best nonfiction books I've read, possibly ever, Warrick's account of the development and growth of ISIS is eye-opening and engaging - I feel very well versed in the history of the organization, but it didn't feel like an information dump. The storytelling was smooth, even as he alternated between places and people. He chose a good mix of firsthand sources, the most fascinating of which were the doctor who treated Zarqawi in Jordanian prison and the Mukhabharat and CIA employees who tracked his transformation into an infamous terrorist. Overall, "Black Flags" was impossible to put down and remains highly relevant for anyone seeking to understand the current international landscape.