The Dark Prophecy by Rick Riordan
A perilous quest to complete. I must become a God again.
I, the god Apollo - cast down to earth in the body of a gawky mortal teen - bravely endured a series of a dangerous trials at Camp Half-Blood.
Now, accompanied by Leo Valdez and the sorceress Calypso (also mortal, ha!), I must find the most dangerous Oracle from ancient times, who may hold the answers I need to return to Mount Olympus.
To make things worse, the second member of the evil Triumvirate - a Roman emperor with a disturbing love of bloodshed - stands in our way.
Without my powers (and good looks and singing voice), how does Zeus expect me to overcome the greatest challenge I've faced in my four thousand years of existence?