Anne of Brittany is nineteen, and duchess of a country under French occupation. Her father died in the invasion that put her on the throne. Charles VIII of France wants to marry her and finish what that invasion started. So Anne secretly betroths herself instead, to Maximilian of Austria. He is the one ruler with an army large enough to make France hesitate.
To cover the arrangement, she leads her court into Brocéliande. It is an ancient forest where the old magic is said to still hold, and where divination fails outright. A unicorn appears where none should. Then a stranger walks out of the trees behind it, turning the hunt into something Anne never planned for.
Katherine Arden sets real fifteenth-century politics against the forest's older rules: kings, papal dispensations, an heiress with no army of her own. Anne's sister Isabeau, the courtier Louis of Orleans, and a peasant girl named Elesbed travel with her. Courtly attraction complicates the plotting as much as any negotiation does.
It is historical fantasy, and the politics carry as much weight as the magic. The forest is where Anne finds out whether she can actually keep the country she is fighting for. A standalone novel.