If you're reading this because you think you might be one, my advice is: close this book right now. Believe what-ever lie your mom or dad told you about your birth, and try to lead a normal life. Being a half-blood is dangerous. It's scary. Most of the time, it gets you killed in painful, nasty ways.
-- Percy (Chapter 1 paragraph Page 1)

Importance: This quote sets the tone for the entire novel, and the series, in that Percy's life is not normal, and those who are like him, including Percy, are in danger for what and who they are.

He said, "You saw her snip the cord.""Yeah. So?" But even as I said it, I knew it was a big deal."This is not happening," Grover mumbled. He started chewing at his thumb. "I don't want this to be like the last time.
-- Grover/Percy (Chapter 2 paragraph Page 29)

Importance: This short exchange is important because it reiterates that Percy is in...