A Court of Thorns and Roses
Feyre and Tamlin begin in captivity and resentment — she's a hunter forced into the fae lands, he's the fae lord who brought her there. Maas builds the hostility carefully before dissolving it, and what makes the transition earn is that Feyre doesn't stop being wary: she comes to trust Tamlin while remaining alert, which is more psychologically honest than most romantasy transitions. The tension continues across the series with Rhysand, who is enemies to lovers on a longer fuse — if anything, the Feyre/Rhysand dynamic in later books is the trope's defining fantasy example. Start here and read the series in order.
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