Shadows

Shadows is a compelling and inventive novel set in a world where science and magic are at odds, by Robin McKinley, the Newbery-winning author of The Hero and the Crown and The Blue Sword, as well as the classic titles Beauty, Chalice, Spindle's End, Pegasus and SunshineMaggie knows something's off about Val, her mom's new husband. Val is from Oldworld, where they still use magic, and he won't have any tech in his office-shed behind the house.
But-more importantly-what are the huge, horrible, jagged, jumpy shadows following him around? Magic is illegal in Newworld, which is all about science. The magic-carrying gene was disabled two generations ago, back when Maggie's great-grandmother was a notable magician. But that was a long time ago. Then Maggie meets Casimir, the most beautiful boy she has ever seen. He's from Oldworld too-and he's heard of Maggie's stepfather, and has a guess about Val's shadows.
Maggie doesn't want to know .