[1] The book covers two major storylines: the killers' evolution leading up to the attack, and the survivors' struggles with the aftermath over the next decade.

Graphic depictions of parts of the attack are included, in addition to the actual names of friends and family (the only exception being the pseudonym "Harriet", which is used for a female Columbine student referred to in Klebold’s journal entries, with whom he was obsessively in love).

His Slate story "The Depressive and the Psychopath" five years earlier, offered the first diagnosis of the killers by the team of psychologists and psychiatrists brought into the case by the FBI.

Formally composed of 53 chapters divided into five parts, the book also includes a timeline, 26 pages of detailed endnotes, and a fifteen-page bibliography organized into topics.

The 'after' story is composed of eight major sub-stories, focused on individuals who played a key role in the aftermath of the attack, including Columbine Principal Frank DeAngelis, alleged Christian martyr Cassie Bernall (another myth, according to the book), "the boy in the window", Patrick Ireland, FBI Supervisory Special Agent Dwayne Fuselier, and the families of victim Daniel Rohrbough and teacher Dave Sanders, who died saving students from the gunmen.

[13] Published by Twelve (Hachette Book Group) on April 6, 2009,[14] Columbine debuted at number seven on the bestseller list for The New York Times in the United States.

[4] The book was very well received by critics, and by news media, which focused heavily on the dispelling of numerous Columbine myths, and also the extensive portrayal of the minds of the two killers.

Jennifer Senior, in The New York Times Book Review, resisted the Capote comparison, but offered high praise.

She observed that: "Had Dave Cullen capitulated to cliché while writing ‘Columbine’, he would have started his tale 48 hours before Eric Harris and Dylan Klebold's notorious killing spree, stopped the frame just before they fired their guns, and then spooled back to the very beginning, with the promise of trying to explain how the two boys got to this twisted pass.

Instead, what intrigues the author are perceptions and misperceptions: how difficult a shooting spree is to untangle; how readily mass tragedies lend themselves to misinformation and mythologizing; how psychopaths can excel at the big con...

I expected a story about misfits exacting vengeance, because that was my memory of the media consensus — Columbine, right, wasn't there something going on there between goths and jocks?

For the same YouTube trailer, Cullen allowed himself to be filmed sitting at his desk amid potted houseplants, scrolling solemnly through a computer-screen copy of one of the killers' hate-filled journals.

Newsweek essay by Ramin Satoodeh stated: "In the decade since Columbine, there have been countless efforts to make sense of that day: memoirs, books, movies, even a play opening in Los Angeles in April.

[46] Further descriptions of the meetings with Wayne and Kathy Harris appear in The Daily Beast feature, "The Last Columbine Mystery," by the same author, published at the time of the paperback release.

[47] The Afterword also includes updates about two bereaved parents and one wounded survivor of the Columbine shootings, and their starkly different perspectives on "forgiveness".

The expanded paperback edition of 2010 also adds scans from the killers' numerous journals,[48] a diagram of the attack,[49] and book club questions.

The author created a free Columbine Teacher's Guide, as well as classroom videos and related material which have been widely downloaded from the internet.