A Darker Shade of Magic by V.E. Schwab
“Are you afraid of dying? Holland had asked him in the alley.
And Kell was. Had always been, ever since he could remember. He feared not living, feared ceasing to exist. Lila’s world may believe in Heaven and Hell, but his believed in dust. He was taught early that magic reclaimed magic, and earth reclaimed earth, the two dividing when the body died, the person they had combined to be simply forfeit, lost.
Nothing lasted. Nothing remained.”