A Serial Killer’s Guide to Marriage by Asia Mackay: Domestic bliss, but make it murderous

What happens when the thing that bonded you as a couple is the one thing you’re no longer allowed to do? A Serial Killer’s Guide to Marriage by Asia Mackay takes that question and runs with it—through marriage, parenthood, suburbia, and the quiet, suffocating boredom that sets in when two people stop working as a team. Readers who enjoyed This Girl’s a Killer will feel immediately at home here, thanks to the same blend of dark humor, moral ambiguity, and sharp observations about womanhood and rage.

Hazel and Fox once believed they were made for each other. Not in a meet-cute, rom-com way, but in a far more specific sense: they are serial killers who take pleasure in killing objectively bad men, saving future victims while satisfying their own darker impulses. Before pregnancy and playdates, their greatest joy came from killing—and from doing it together. Their intimacy was built on absolute trust, shared secrets, and a kind of moral clarity that only made sense to the two of them (and me, to be honest).

Hazel and Fox once believed they were made for each other. Not in a meet-cute, rom-com way, but in a far more specific sense: they are serial killers who take pleasure in killing objectively bad men, saving future victims while satisfying their own darker impulses. Before pregnancy and playdates, their greatest joy came from killing—and from doing it together. Their intimacy was built on absolute trust, shared secrets, and a kind of moral clarity that only made sense to the two of them.

Then Hazel gets pregnant, and everything changes. Fox decides the killing must stop to protect their future child from the very real possibility of losing both parents to prison. It’s a rational decision. It’s also the beginning of the end. When the killing stops, so does the teamwork. Instead of supporting each other through withdrawal from the one thing that made them feel alive, Hazel and Fox splinter off into separate, often unhealthy coping mechanisms. The result is a marriage slowly rotting from the inside.

Hazel and Fox begin keeping things from each other that don’t seem like they should require lies, but once the habit of withholding starts, it spreads fast. Hazel even begins to suspect Fox of cheating on her, of buying a second home to start over with someone else. The paranoia feels extreme—until you remember these are people whose former hobby required constant vigilance and distrust. When your shared language disappears, suspicion fills the gap.

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What makes the novel work as well as it does is that Hazel and Fox genuinely adore their daughter. Parenthood doesn’t magically turn them into different people; it simply raises the stakes. Mackay refuses the comforting lie that settling down erases who someone fundamentally is. Hazel’s murderous itch isn’t a phase—it’s part of her. Fox’s need for control and foresight doesn’t vanish with diaper changes. Love, in this book, is real, but it’s not curative.

That said, there are moments where the story strains its own logic. A few plot holes pulled me out of the novel—questions of timing, behavior, or consequence that felt less like intentional ambiguity and more like things a strong editorial pass should have caught and helped smooth out before publication. They don’t ruin the book, but they do interrupt the immersion at key moments, especially for attentive readers.

However, there’s also a quieter, more unsettling undercurrent running through the story. Hazel and Fox once targeted men who harmed women, and reading it in a world shaped by domestic violence and human trafficking raises uncomfortable questions. How often do we pass by someone who needs help without noticing? How many doors hide horrors we never see? Mackay doesn’t glorify vigilante violence, but she does leave you wondering whether there are people out there quietly doing what Hazel and Fox once did. And whether that idea should be comforting or terrifying (I choose to be comforted).

Darkly funny, sharply observant, and more emotionally grounded than its premise suggests, A Serial Killer’s Guide to Marriage is less about murder than it is about intimacy—and what happens when a couple stops working as a team. Despite its flaws, it’s a clever, unsettling read that will appeal to fans of morally complicated thrillers with something sharp to say about modern marriage.

Have you read this one? I’d love to hear whether you found yourself rooting for Hazel and Fox—or recoiling from them entirely. Share your thoughts in the comments.

If you loved A Serial Killer’s Guide to Marriage, be sure to check out my full list of Books About Women Serving Up Justice to Bad Men on my independent online bookstore!

Related Content

• Interview with Asia Mackay: Author of A Serial Killer’s Guide To Marriage (Goldsboro Books)
• Q&A: Asia Mackay, Author of A Serial Killer’s Guide To Marriage (The Nerd Daily)
• From mum to Killing It – Asia Mackay’s journey to publication (Professional Writing Academy)
• The book you’ll be dying to read: A Serial Killer’s Guide to Marriage by Asia Mackay (Papyrus and Peppermint)

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