The characters include Alex Cormier, a superior court judge; her daughter Josie, a junior in high school; Lacy, Lewis, and Peter Houghton; Detective Patrick Ducharme; and several victims-to-be.

After passing several dead and wounded victims, Patrick traps and arrests the shooter, Peter Houghton, in the locker room, where he finds two students, Josie Cormier and Matt Royston, lying on the floor surrounded in blood.

The friends slowly drifted apart as they got older: Josie joined the popular crowd in order to protect her own interests, seeing her relationship to Peter as embarrassing.

When Joey is killed in a car accident in 2006, Lacy and Lewis Houghton are too upset to pay attention to their remaining son, causing a bigger rift between Peter and his parents.

In their sophomore year, Josie begins dating Matt, a popular jock who leads his friends Drew Girard and John Eberhard in bullying Peter.

In the final stage of the trial, Josie reveals that she was the one who shot Matt the first time in the stomach after grabbing a gun that fell out of Peter's bag.

At the end of the book, one year from the date of the massacre, Josie has received a five-year sentence for accessory of manslaughter and is regularly visited in jail by her mother.

The cafeteria, the gym and locker room where the massacre took place have been replaced by a large glass atrium with a memorial to the dead in the center, a row of ten white chairs bolted to the floor.

In order of death: The book received generally favorable reviews by critics, for the writing, character development,[2] plot twists, and the moral issues raised, including peer pressure, popularity, self-image, school bullying, betrayal and deception, sexual orientation doubt, teen dating violence, suicide, video game violence, single parenthood and communication barriers between adolescents and adults.

"[2] The Free Lance-Star mentioned that Nineteen Minutes created a two-sided story that helps readers understand everything about the school shooting, which is more than what normal media coverage will provide about this type of tragedy.

[7] The Boston Globe considered Nineteen Minutes "an insightful deconstruction of youthful alienation, of the shattering repercussions of bullying, and the disturbing effects of benign neglect.

"[8] An ambiguous point in the story is the identity of the author of the handwritten journal entries at the start of the book chapters, with New York Times saying this writer may or may not be Peter, although "it doesn't sound like him",[6][9] and Hippo Press analyzing that whether or not the writer is identified "doesn't matter"; the author may be either Josie or Peter, and the point is that the diary pieces "provide insight into the workings of the teenage mind", showing that they are "not all that different.