Tender Cruelty by Katee Robert

The barrier that’s protected Olympus for generations has fallen. The enemy’s breached the gates and the Thirteen are scrambling to protect themselves, their loved ones, and the city they’ve sworn to protect. At least they would be if they weren’t at each others’ throats instead.
Hera has no intention of letting her husband, Zeus, survive the oncoming storm. But despite the white-hot hatred burning between them, when Hera and Zeus are forced to work together, enmity crystalizes into something brighter. Hotter. Too powerful to deny or destroy.
Hera never bartered on falling in love with the man she married—the man she once swore to kill. But now, standing back-to-back in the ruins of Olympus, she may be forced to admit that she’s been wrong about Zeus all these years…and there may be something about their marriage worth saving if they can survive long enough to turn sworn enemies into something more.