Beautiful Chaos (Caster Chronicles #3) by Kami Garcia + Margaret Stohl

ETHAN WATE IS IN LOVE WITH A CASTER GIRL.
WHEN HE LOOKS AT LENA, IT'S LIKE THERE'S NO ONE ELSE IN THE WORLD.

But Ethan is mortal, and on her seventeenth birthday Lena made a choice that changed everything. The girl Ethan loves has broken the world with the supernatural powers she is struggling to control . . .

Now, if they are to fix the chaos Lena has caused, one of them must make a terrible sacrifice. Sometimes there isn't just one answer. Sometimes there's no going back. And this time there won't be a happy ending.