The Summer War — Naomi Novik

In this poignant, heartfelt novella from the New York Times bestselling author of Spinning Silver and the Scholomance Trilogy, a young witch who has inadvertently cursed her brother to live a life without love must find a way to undo her spell.

Celia discovered her talent for magic on the day her beloved oldest brother Argent left home. Furious at him for abandoning her in a war-torn land, she lashed out, not realizing her childish, angry words would suddenly become imbued with the power of prophecy, dooming him to a life without love.

While Argent wanders the world, forced to seek only fame and glory instead of the love and belonging he truly desires, Celia attempts to undo the curse she placed on him. Yet even as she grows from a girl to a woman, she cannot find the solution -- until she learns the truth about the centuries-old war between her own people and the summerlings, the immortal beings who hold a relentless grudge against their mortal neighbors.

Now, with the aid of her unwanted middle brother, Celia may be able to both undo her eldest brother's curse and heal the lands so long torn apart by the Summer War.