By Dave Cullen. Published in 2009.

Dave Cullen taught me the difference between hate and contempt. Some five years ago, he wrote an article for Slate exploring the motives of the notorious Columbine killers, Eric Harris and Dylan Klebold, with new analysis from the FBI’s lead investigator on the case, a clinical psychologist. The key idea was that the two boys were very different people: Harris was a full-blown psychopath (in the true psychiatric sense), and Klebold was a suicidal depressive who fell into the other boy’s orbit.

That conclusion and the well-informed rationale behind it are fascinating, but it was the distinction between hate and contempt that haunted me. In the immediate aftermath of the massacre, most people assumed that the killers’ motive was hatred—for jocks, for minorities, for Christians, whatever—but judging from the considerable evidence left behind, Harris, the mastermind, wasn’t motivated by hatred of individuals or even of specific groups. In a way, that would have required acknowledging his victims as human beings, fellows worthy of hate. Harris considered himself a god among insects; his victims were interchangeable fodder for his apocalyptic vision. In short, he didn’t feel hate so much as general contempt. And that’s what makes him so frightening.

Cullen expands upon that old article—along with his numerous others and a decade’s worth of investigation into the attack—to produce Columbine, an exhaustive, compelling look at that horrific day in April 1999, the months that lead up to it, and the years that followed. At once a true crime tome, a psychopathy primer, and a media criticism treatise, the book is engrossing and deeply thought-provoking. That unforgettable lesson on hate and contempt is not an anomaly: Columbine is not a rubber-necking tabloid tale but a reflective, compassionate view of both the trees and the forest. As the New York Times acknowledged, Columbine isn’t In Cold Blood reborn (which cracked me up: Capote’s masterpiece is truly the unattainable grail of the true crime genre), but by virtually any other standard, it’s a triumph.