The Burning Maze (The Trials of Apollo Book 3)

He was a God once. Until he was cast out his father, Zeus. Now, he's an awkward teenager. Called Lester.
The only way out is a series of scary and dangerous trials, of course.
For his third trial, Apollo must journey through the Labyrinth to free an Oracle who only speaks in puzzles.
Then, defeat the most vicious of three very vicious Roman Emperors.
(All without the use of his godly powers.)
It looks like he will need all the help he can get - from some new and old friends.