Lord of the Flies is such a wonderful story. It has many themes, all of which are true. My favorite chapter is Chapter 11 in which Ralph, Piggy, and Samneric (Sam and Eric; they are twins but they do everything together, so the boys refer to them as one person) confront Jack, Roger, Robert and the rest of the savages. Ralph and Jack get into a fight, Piggy dies holding the conch, and makes some pretty good points.
It has many symbols as well: Piggy's glasses = Piggy's logic (glasses are seen as the extra lens to see things clearly and logically), the conch = power, Jack and the hunters = the beast contained in all of us that sometimes we can't see.
All in all, just an excellent, excellent book.