Shadow and Bone (The Shadow and Bone Trilogy, 1) by Leigh Bardugo

The story follows Alina Starkov, a young orphan and mapmaker in the army of Ravka, a nation torn apart by war. When her regiment is attacked while crossing the Shadow Fold, a region of impenetrable darkness filled with monsters, Alina discovers a dormant power within her that could be the key to saving her country. She is thrust into the world of the Grisha, the magical elite, and taken under the wing of the mysterious and powerful Darkling, who believes Alina could be the Sun Summoner—a prophesied figure who can dispel the Shadow Fold. As Alina learns to harness her power, she is caught between her growing feelings for her childhood friend Mal and the seductive allure of the Darkling. However, not everything is as it seems, and Alina must navigate a web of deception and betrayal to uncover the truth and determine her own destiny.