Broken God by Nazarea Andrews

Power is a strange and broken thing.

He was the sun god, the god of healing and song. And prophecy.

Apollo has lived alone for centuries, content to spin out the years wandering a new and strange world, lost in the past and endless versions of the future. He has cut all ties with the remains of Olympus and his power, and hidden himself in humanity. His twin thinks he’s depressed, spending his time in coffee shops, hospital waiting rooms, and concert halls…and nothing matters. Not really.
Until her. Iris. With her teasing mouth and soulful music and eyes that remind him of the past.

He can’t resist her smile. A girl as wild as he was, once, with a poet’s tongue and the body of a siren, who for one night makes him forget all the years and everything he gave up.

And he can’t stop fate. Gods knows he’s tried. He can’t help taking her. Even if he knows better.
When Iris wakes up screaming, caught up in visions of the future, Apollo realizes that he didn’t leave his power quite as far behind as he thought.
He’s the god of prophecy and he’s been running from it, for centuries.

Iris is everything he has to avoid. Now he has a furious Oracle on his hands, his sister trying to fix him, and someone is killing the gods.
It’s not just his tenuous sanity that hangs in the balance this time. It’s all of Olympus. Godhood really wasn’t supposed to be this hard.