Behooved by M. Stevenson

A charming slow-burn romantasy featuring a duty-bound noblewoman with a chronic illness, a prince who would rather be in a library than on a throne, and a magical ride through a world of cozy enchantment

Bianca knows her duty comes before her heart. So when the threat of war looms, she agrees to marry the neighboring kingdom’s heir. But not all royal weddings are a fairytale, and Prince Aric, Bianca’s betrothed, is cold, aloof, and seems to hate her on sight.
To make matters worse, on their wedding night, an assassination attempt goes awry—leaving Aric magically transformed into a horse. Bianca does what any bride in this situation would do: she mounts her new husband and rides away to safety.
Sunset returns Aric to human form, but they soon discover the assassination attempt is part of a larger plot against the throne. Worse, Bianca has been framed for Aric’s murder, and she’s now saddled with a husband who is a horse by day and a frustratingly attractive man by night.
As an unexpected romance begins galloping away with their hearts, Bianca and Aric must rely on each other to unravel the curse and save the throne.