The Lord of the Flies could be read as one big allegorical story. An allegory is a story with a symbolic level of meaning, where the characters and setting represent, well, other things, like political systems, religious figures, or philosophical viewpoints. Let's try a sample:
See how it's done? Of course, you could argue with this breakdown. Maybe Simon represents the religious side of humanity; maybe Jack represents cruelty, or maybe Roger does. But the point is that they're not fully developed and rounded characters so much as they are symbols.
The only time we pull out of the allegory is at the very end of the novel, when the other "real" world breaks through the imaginary barrier around the island. Yet this is also the moment when the real question of the allegory hits home: who will rescue the grownups?