The Tyrant’s Tomb (The Trials of Apollo #4) by Rick Riordan
Things are getting very bad, very fast, for Apollo…
The former God Apollo is having a pretty rough time of it. Well, for one thing, he’s been turned into a human and banished from Olympus. And he’s called Lester. But being an awkward mortal teenager is the least of his worries right now.
Though he and some of his friends have emerged from the Burning Maze, they still have a triumvirate to defeat, oracles to rescue and prophecies to decipher, so that the world may be saved, and Lester can become Apollo once again.
But, right now, Caligula is sailing to San Francisco to deal with Camp Jupiter personally, and they have to get there first. Failure to do so would risk its destruction . . .