This is an amazing and horrifying book that not only gives an account of the massacre at Columbine High School in '99 but the onset and the aftermath as well. Cullen reported on the tragedy the day of the shooting, but it's taken him nine years to research and compile this book, which is thorough, dispels many myths, and brings to light information that has only recently been released. 
 I listened to this audio-book, though I want to re-read it in "actual" book format. Cullen doesn't approach the story chronologically and this organization was, at first, frustrating and difficult to tell when he was switching between times and characters; however, once I got to know the ten or so characters he was focusing on, it was much easier, and about a quarter of the way through reading the book I was thankful he organized it that way. It was hard enough--emotionally--to listen to the shot-by-shot account of the massacre, but I don't think I'd have been able to listen to it at all if it had been built up to for seven or thirteen hours and then came at the middle or the end (another reason I want to read the hard copy is so that I can clarify some timeline questions I have but skip some of the more gruesome sections). Also, by breaking up the massacre into bits and splicing them among stories about the planning leading up to the event and the survivors and community dealing with the aftermath, Cullen's story is much richer and I got a very full sense of each character and of the school and community themselves. 
 Cullen's writing is both poetic and objective. He uses the third person when writing about the media throughout the book, and it feels well removed. Too much--or any--first person would have made it feel overly sentimental and perhaps exploitative. There are still questions left unanswered, but I feel like I've got a handle on what happened and why it happened, which is some small sort of consolation. 
 This took me a very long time to get through because of the subject matter. It's a tremendously difficult book to read, but it's something that I feel everyone should read.