to feel I had a home in cabin eleven and I might be a normal kid—or as normal as you can be when you're a half-blood—I'd been separated out as if I had some rare disease.

This chapter marks the continuation of Percy's struggle with his identity as a half-blood and the son of Poseidon, one of the Big Three gods. When Grover comes to fetch Percy to go see Mr. D, Percy thinks:

I figured it was a crime for me just to be alive.

Dionysus seems to reflect that negativity back to Percy, as he cruelly states:

If I had my way . . . I could cause your molecules to erupt in flames We'd seep up the ashes and be done with a lot of trouble. But Chiron seems to feel this would be against my mission at this cursed camp: to keep you little brats safe from harm.

During this chapter, Percy also gets confirmation that conflict is raging between Poseidon and Zeus. Zeus thinks that Poseidon has stolen his master bolt in order to have the Cyclops construct illegal copies of it in order to eventually stage a coup against Zeus and dethrone him. Zeus believes that Percy himself may have been responsible for sneaking into Olympus and stealing the weapon on behalf of his father. The war that may break out as a result is described as follows:

Imagine the world in chaos. Nature at war with itself. Olympians forced to choose sides between Zeus and Poseidon. Destruction. Carnage. Millions dead. Western civilization turned into a battleground so big it will make the Trojan War look like a water-balloon fight. 

I think that the opening chapter has some great quotes that are important to the story and Percy himself.

Look, I didn't want to be a half-blood.

The previous quote is the first line of the book. It's important because it shows readers that Percy didn't choose to be a half-blood in the way that Bella Swan chose to become a vampire. Instead, Percy's lineage has been thrust on him, and he has no choice in the matter. He can absolutely try to ignore his lineage, but that ultimately doesn't change anything. He is what he is, and he has to accept it.

Another good quote follows shortly after the previous quote.

Being a half-blood is dangerous. It's scary. Most of the time, it gets you killed in painful, nasty ways.

This is an important tie-in with the previous quote because it shows readers a couple of things. We have no idea what a half-blood is or what it means, but this quote all of a sudden shows readers that it is likely a bad thing. Additionally, the wording of the quote hints at the idea that the narrator is speaking from personal experience. It's telling us that he has been in those situations and has lived to tell about it.

In addition to being a half-blood, Percy has really low self-esteem about himself, and readers are clued into this fact with the following quote.

I wondered how she could say that. What was so great about me? A dyslexic, hyperactive boy with a D+ report card, kicked out of school for the sixth time in six years.