You can read the Goodreads summary here.
This book started off very intense. For the first third of the book I couldn't read more than a couple chapters at a time. The descriptions of the event itself lumped in the beginning of the book made me nauseated. They made me cry - and I mean that in a good way because they were very well written and presented the facts clearly and definitively. If you want to know what really happened, this is the book you need to read.
About halfway through the book the author got more into the media spin and general misconceptions about the event, which I found very interesting. Sure enough, most of what I thought had happened were misconceptions about the boys, their motives, what went down, and also the myth of what happened to Cassie Bernall in the library...
I was twelve years old when "Columbine" happened and was at a brief period in my life when I was active in church. In the book, Cullen talks about the differences between the Evangelicals in the area and the mainline protestants. The Evangelicals had (and still do) see Cassie as a martyr who told Eric that she believed in God and that's why he shot her. Columbine brought to light that that exchange never happened. The book Cassie's mother wrote, She Said Yes, was published despite the fact that the police, as well as the publisher, knew the story was false. I'm Lutheran (thus mainline) but when I was in youth group at the time, Cassie's book was passed around among us. Several of us borrowed it, read it, and as impressionable youth, took it as fact. I don't remember much about She Said Yes today, aside from the famous and false exchange, but I can't help but feel lied to now.
I enjoyed the books writing style. It read like a novel at some points but presented copious fact. It's obvious Dave Cullen spent a vast amount of time researching; there are endnotes and a bibliography attesting to that. I believe he presented everything fairly and the story really opened my eyes. Eric and Dylan weren't just a couple of kids from the Trench Coat Mafia who hated the jocks and targeted some kids. It went way beyond that. To say it's disturbing is an understatement. The book gets five stars from me and I would recommend it to anyone remotely curious about what really happened in Littleton.
What I wish had been included, and granted this is probably something small and seemingly unimportant - but after all of the evidence was released, what did Harriet think about Dylan's writings about her? I can't imagine.