What is the main problem for book The Sea of Monsters?

The main problem in Rick Riordan's *The Sea of Monsters* is the theft of the Golden Fleece. This theft leaves Camp Half-Blood vulnerable to attack by the monstrous Titan, Kronos, who wants to use the fleece to gain power and break free from his imprisonment.

Here's why this is the main problem:

* It directly threatens the safety of Camp Half-Blood: Without the Fleece, the camp's magical defenses are weakened, leaving the demigods vulnerable to Kronos' forces.

* It sets in motion the entire plot: The quest to retrieve the Fleece drives the narrative, leading Percy Jackson and his friends on a dangerous journey.

* It introduces a significant threat to the demigod world: The threat of Kronos' return and the potential for his rise to power is a major concern for all demigods.

While the book explores other themes, such as friendship, loyalty, and self-discovery, the theft of the Golden Fleece serves as the central conflict and the driving force behind the story.