Set in a world of perilous magic and moonlit forests, this seductive romantic fantasy tells the story of a defiant changeling, her cursed sister, and the dangerous fae lord she must defeat to save her family. In a kingdom where magic has been lost, Fia is a rare changeling, left behind by the wicked Fair Folk when they stole the High Queen's daughter and retreated behind the locked gates of Tír na nÓg. Most despise Fia's fae blood. But the queen raises her as a daughter and trains her to be a spy. Meanwhile, the real princess Eala is bound to Tír na nÓg, cursed to become a swan by day and only returning to her true form at night. When a hidden gate to the realm is discovered, Fia is tasked by the queen to retrieve the princess and break her curse. But she doesn’t go with her is prince Rogan, Fia's dearest childhood friend—and Eala’s betrothed. As they journey through the forests of the Folk, where magic winds through the roots of the trees and beauty can be a deadly illusion, Fia’s mission is complicated by her feelings for the prince…and her unexpected attraction to the dark\-hearted fae lord holding Eala captive. Irian might be more monster than man, but he seems to understand Fia in a way no one ever has. Soon, Fia begins to question the truth of her mission. But time is running out to break her sister's curse. And unraveling the secrets of the past might destroy everything she has come to love.

On a mysterious snowy island ruled by a trickster king where magic comes at a price, a deadly trial commences. The prize: a chance for vengeance. After her sacrifice on the Ember Moon, Fia is flush with powerful magic and eager to rush into battle against her murderous sister, Eala. However, Fia’s new husband Irian suggests they bide their time and retreat to the Silver Isle, a snowy island at the edge of the fae world. Ruled by the cunning smith\-king, the Silver Isle proves far from a safe haven. Fia and Irian become embroiled in the Tournament of Kings competing for a magical forging of immense power. Their relationship will be put to the test as they navigate their conflicting motivations, shifting allegiances, and ancient magic. With the end of the tournament looming and Eala’s threat growing, Fia must decide just how much she’s willing to sacrifice to defeat her sister.

A Heart So Green is the enchanting conclusion to the Number One Sunday Times bestselling Fair folk trilogy, perfect for fans of The Knight and the Moth and Fourth Wing. After the explosive finale of the Tournament of Kings, Fia and Irian manage to escape to the wildlands, dodging pursuit by Fia's cunning sister Eala. With Fia locked in her own mind, battling a powerful celestial entity; Irian must form new alliances to come up with a plan to defeat Eala's terrifying magic. With both the human and fae realm under threat, Fia and Irian must pursue their dangerous plan, no matter the cost. On Bealtain Eve, when the veil between worlds is at its thinnest, they will finally face off against the swan princess and forge the ending to their love story that was written in the stars.