The Girl Who Drank the Moon by Kelly Barnhill

With more than a million copies sold, Newbery Medal winner The Girl Who Drank the Moon is a must-read for fans of classic children's literature or timeless fantasy fables.
Every year, the people of the Protectorate leave a baby as an offering to the witch who lives in the forest. They hope this sacrifice will keep her from terrorizing their town. But the witch in the Forest, Xan, is kind. She shares her home with a wise Swamp Monster and a Perfectly Tiny Dragon. Xan rescues the children and delivers them to welcoming families on the other side of the forest, nourishing the babies with starlight on the journey.
One year, Xan accidentally feeds a baby moonlight instead of starlight, filling the ordinary child with extraordinary magic. Xan decides she must raise this girl, whom she calls Luna, as her own. As Luna's thirteenth birthday approaches, her magic begins to emerge-with dangerous consequences. Meanwhile, a young man from the Protectorate is determined to free his people by killing the witch. Deadly birds with uncertain intentions flock nearby. A volcano, quiet for centuries, rumbles just beneath the earth's surface. And the woman with the Tiger's heart is on the prowl . . .
After you finish The Girl Who Drank the Moon, look for Kelly Barnhill's latest wondrous fantasy for young readers, The Ogress and the Orphans!