The Lightning Thief by Rick Riordan
Chapter 10: I Ruin a Perfectly Good Bus

The beginning of Percy’s quest goes about as well as expected considering his status as a wanted criminal/suspect.

The Lightning Thief by Rick Riordan
Chapter 9: I Am Offered a Quest

After spending about four chapters explaining Percy’s new reality and how this world works, it’s finally time for Percy to leave the dwindling safety of Camp Half-Blood and try to fix other people’s problems that quickly become his problems, like a true Greek hero.

The Lightning Thief by Rick Riordan
Chapter 8: We Capture a Flag

Before we get to the series staple war game, there’s still a bit more exposition left in the first half of the chapter.

The Lightning Thief by Rick Riordan
Chapter 7: My Dinner Goes Up in Smoke

This is the third straight chapter of (possibly) necessary exposition. Luckily, this chapter is less showing off Camp Half-Blood and more laying down the basics of the book’s plot.