Once Upon a Demon’s Heart

Name: Once Upon a Demon’s Heart
Author: K.M. Moronova

Top 200 · #189 in Enemies to Lovers Romance on Amazon

K.M. Moronova

Book 1 in the Cruel Fates Duet series · Reading order →

SpiceDarkness

How we rate spice & darkness

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Spice & darkness rated — content warnings listed below

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Why we recommend it

The fairy tale premise is inverted: once upon is ironic, the demon's heart is the prize, and the story is about what it costs to get it. Moronova writes the dark romantasy with deliberate fairy tale scaffolding — the structure is familiar, the contents are not, and the romance is built on the worst possible chemistry.

At a glance

Once Upon a Demon’s Heart is a dark romantasy by K.M. Moronova. With 3/5 for spice and 4/5 for darkness it sits mid-range for dark romantasy (of the 648 dark romantasy books on Readark, 34% rate lower for darkness and 8% lower for spice). Its tropes include forbidden romance and morally grey MC. It is about as dark as K.M. Moronova’s other books on Readark (average darkness 4.0/5). We have not tagged its content warnings yet, so check the author’s notes before you start.

Tropes

Forbidden Romance Morally Grey MC

Book details

Published: January 2025

Once Upon a Demon’s Heart spice level

Once Upon a Demon’s Heart is rated 3/5 for spice on Readark’s scale: open door, meaning explicit scenes written plainly, but not the engine of the book. Its darkness rating is 4/5: heavy, meaning sustained cruelty, trauma or non-consent central to the relationship. How we rate