The novel opens with narrator Jessica Morton, a junior at Helshire College and a member of an age-old crime family, taking Peter, her younger cousin and fellow Helshire student, on a climb—no, not the recreational kind. It’s actually a midnight trek up the school’s tallest building, from which Jessica ensures, at Grandmother’s orders, that Peter will plummet to his death. (Peter had “fallen into disfavor” with the family.) “My first kill, before I’d even graduated,” Jessica thinks with satisfaction after she’s completed her assignment. At Peter’s funeral, which is at the Morton estate in upstate New York, Jessica, who is bisexual, becomes smitten with Hiromi Kennedy, a Japanese American artist she will get to know during a summer internship at a New York City gallery. The job leads to a cascading series of events of spectacular consequence to Jessica, Hiromi, and the extended Morton clan. This first collaboration between the married Larbalestier and Westerfeld, who are best known for their YA novels, serves up a robustly imagined world that stops just short of heightened but abounds with nods to horror and macabre symbolism (bones, the color red). While the authors’ attention to atmospherics pays dividends, there’s an oddly persistent slackness to the storytelling, and given how much work is required of readers to keep track of Mortons living and dead, their motivations, and their secrets, to say nothing of their specialized argot, this long book is a heavy lift. Jessica may exude Wednesday Addams cool, but she’s introduced as an unrepentant murderer, and some readers may not stick around for her crisis of conscience, which is to say her realization that she may actually have one.