Rebecca by Daphne Du Maurier (Anniversary Edition.)

After centuries of sleep, the gods are warring again. But eighteen-year-old Iris Winnow just wants to hold her family together. Her mother is suffering from addiction and her brother is missing from the front lines. Her best bet is to win the columnist promotion at the Oath Gazette.

To combat her worries, Iris writes letters to her brother and slips them beneath her wardrobe door, where they vanish—into the hands of Roman Kitt, her cold and handsome rival at the paper. When he anonymously writes Iris back, the two of them forge a connection that will follow Iris all the way to the front lines of battle: for her brother, the fate of mankind, and love.