Dave Cullen (2009)
Author Dave Cullen spent ten years researching the 1999 school shooting at Columbine High School. The result is an absorbing narrative account of the event, the aftermath, criminal investigation and, most disturbing, the motive. Cullen’s book reveals many shocking truths, separating the myths (and there are many) from reality. Columbine reveals a cover-up by law enforcement, the many missed warning signs, and a chilling portrait of psychopathology. While this book doesn’t have quite the literary flair of say, In Cold Blood, it goes miles beyond a dry recitation of facts to paint a compelling portrait of a community in crisis.
2 Things @ Once 
Thanks for the very kind words on my book.
We’ve had a lot of interest from teachers—and students—on using the book in school, so we’re trying to make that easier. I spent a good chunk of the fall creating the Columbine Instructor Guide and Columbine Student Guide. They are now online and free. Please consider spreading the word. Thanks.
Cullen , who first reported on the story for the online magazine Salon, acknowledges in the book’s source notes that thoughts he attributes to Klebold and Harris are conjecture gleaned from the record the pair left behind.
Jeff Kass takes a more straightforward approach in “Columbine: A True Crime Story,” working backward from the events of the fateful day.
The Denver Post
Mr. Cullen insists that the killers enjoyed “far more friends than the average adolescent,” with Harris in particular being a regular Casanova who “on the ultimate high school scorecard . . . outscored much of the football team.” The author’s footnotes do not reveal how he knows this; when I asked him about it while preparing this review, Mr. Cullen said he did not necessarily mean to imply that Harris was sexually active. But what else would such words mean?
“Eric and Dylan never had any girlfriends,” the more sober Mr. Kass writes, and were “probably virgins upon death.”
Wall Street Journal