Everything in this book is a symbol.
But I suppose I cannot just leave my post like that.
I will name several and elaborate on them, but I cannot promise that they will be even sort of connected in any way, shape, or form.
Let's begin with the island. When they had first arrived, the island seemed peaceful, a place of refuge, but also very scary, since they felt they were not meant to be there. Then, as time went on, the island began to feel more like a home, as Ralph says. However, Ralph in particular still feels that the island is still trying to get rid of them, but is maybe biding its time. He describes it as a leviathan, which even when disregarding the connotations from Supernatural is still not usually going to be a good thing. He could have described the island as a peaceful giant, or a sleeping one, but he used the word "leviathan". So Ralph still thinks the island is out to get them. As for the other boys, it is not often that the story is told from their point of view, but one can assume that they feel the same way.
Next up for analysis is Ralph, since he was just mentioned. Ralph has also seen a bit of change, though he hasn't really changed all that much. He is less of the fair prince now than he was, since everyone used to look up to him. Now people sort of still look up to him, but he has fallen in a way, since he wants so badly to be like the adults, with his haircuts and soap and obsessing over his fingernails, and the other boys are starting to forget about their old life and settle in. Their lives are referred to as past and present. They are living on an island and they will probably all eat each other. But Ralph still wants to go back to England, which he still refers to as home, despite the fact that the island is also home. I don't know. I did say it probably wouldn't make sense.
Finally, we have Simon. Nope, there is nothing connecting this with the last paragraph. Simon is just my favorite. He's all adorable and helpful and British and I just really like him. He definitely represents religion, which we saw at its most obvious when Ralph pushes Simon away and returns to his own personal hell. Basically saying that it is absolutely certain that Simon is religion, because when you push religion away, you will go to a hell designed specifically for your punishment purposes. Simon also frequently sneaks away to meditate in his little room...with a rug in the center that is hit by a perfect beam of sunlight...and candles all around to make it all smell good like incense...yeah. So Simon most definitely represents a Christ figure or a Buddha figure. He is religion. Also, all the boys rejecting Simon as a person symbolizes their own gradual descent away from society and religion. They starting chanting about killing pigs, for goodness sake. They have definitely rejected religion, both literally and symbolically.
There we have it. Three random symbols plucked from the book and analyzed.