The Trials of Apollo #1: The Hidden Oracle
The adventure begins again as the god Apollo is stripped of his immortality—and sent to live in New York City! He can think of only one demigod who can help him... Percy Jackson!
How do you punish an immortal? By making him human, of course! After angering his father, Zeus, the god Apollo is cast down from Olympus. Weak and disoriented, he lands in New York City as a regular teenage boy. Now, without his godly powers, the 4,000-year-old deity must learn to survive in the modern world until he can somehow find a way to regain Zeus's favour.
But Apollo has many enemies—gods, monsters, and mortals who would love to see the former Olympian permanently destroyed. Apollo needs help, and he can think of only one place to go…an enclave of modern demigods known as Camp Half-Blood.