To 16-year-old Petula de Wilde, optimists are misguided. They are people who believe things will always go their way and don’t see danger until it’s too late. When her toddler sister dies in a random accident, Petula learns three things: 1) Life is not fair. 2) Tragedy can strike when you least expect it. And 3) Always expect the worst. That way you might have a chance of protecting yourself and the ones you love.

And so, Petula becomes a dedicated pessimist. A pessimist is a realist. A pessimist stays safe. Petula spends hours in front of her computer, hunting down articles about the most unusual and unexpected deaths. And while collecting stories about freak accidents seems to soothe her in the moment, most of her consciousness is consumed with unyielding vigilance. What she eats, whom she touches, even her route home from school is affected. For Petula, defensive pessimism is a coping mechanism, and it gives her a sense of control over uncontrollable events. But ultimately, all this constant caution brings more anxiety than relief, and she finds herself alone with her worries more often than not.

Then, over the course of the school year, things start to change for Petula. She allows her shell to be cracked – by an avuncular principal, by the quirky outcasts in her Youth Art Therapy group, and, most significantly, by the new boy with the mechanical arm and mysterious past.

Jacob Cohen is just the right side of good looking, and uncomfortably observant. His enthusiasm for life annoys Petula as much as his uncanny ability to see through her protective layers. When they are thrown together on a school project, Petula lets down her guard and starts to fall for both the boy and his way of seeing the world. Petula looks to Jacob to feel safe, until she discovers he may not be exactly what he seems. Could that sunny demeanor and positive outlook be Jacob’s protective shell?

Optimists Die First is Nielsen’s fifth novel, and her best work to date. Given her critical and commercial success in the world of Canadian kidlit as a middle-grade writer, that’s no small achievement. The author does a brilliant job subverting expectations. For most of the novel, Jacob’s character exists solely to teach Petula how to embrace life and its infinite mysteries. He is the male version of a Manic Pixie Dream Girl, and it’s refreshing to see gender stereotypes turned on their head in this manner. The emotional journey is assigned to the female character, and the supporting role to the male. Jacob is portrayed as a wannabe filmmaker, who often uses plots from movies to fill in for his own life story. He acts out a filmic, clichéd, love-interest trope to cover up his own pain, using the MPDG facade to avoid dealing with reality.

But make no mistake: this is a love story. Optimists Die First is full of all the anticipations and excitements of a first romance. And while there are no squishy details, there is a positive, respectful portrayal of sex I wish was written a whole lot more often.

However, the book is most interesting as a story of guilt and its relationship to grief. This could easily be yet another YA novel where Bad Things Happen. But depite being intense, the subject matter isn’t overly heavy, and Nielsen’s background in TV writing shows: the dialogue is effortless, the plot moves at a fast pace, and the scenes come alive. Nielsen’s wise choice to set the book nearly two years after the central tragedy saves it from being carried by raw emotion and pain, instead presenting a poignant exploration into the nuances of healing. Coping is complicated, and Nielsen never pretends that’s not true.