That went pretty quick

Well, I finished Lord of the Flies and I have to say that I'm disappointed. The ending was so abrupt. Ralph is being chased by everyone on the island and just runs into a naval officer who happened to see the fire. Unfortunately, I didn't get the full enjoyment out of this book because I had it ruined for me. After the first two days of having this book and only reading the first two chapters, I had learned that simon died, Piggy died, and a ship came in the end. In fact, I was sitting in the hall reading after track, and someone who I barely know walks by me and says, "Piggy dies." What is it about this book that makes people want to ruin it?