Just saw this movie...
...and I liked it A LOT, I'm going to read the book and watch the 90's adaptation as soon as I can.
What impressed me the most is that it nails human nature almost perfectly.
I've read some other messages on the board and many say that the author's intent was to depict the inherent evil potential of human beings, but I think that a more complete view would be to say that the movie (and I guess the book too) portraits the inherent animal/beastly nature of human beings.
If you think about the evolution of the human specie, you can easily imagine how the raw nature of someone like Jack would've been very useful back in the day, when humans had to face quite real beasts and not just imagined ones.
Nowadays people don't really have to face tigers hunting them, but the instinct is still there and still strong - it's the beast within us the movie talks about, and it shapes our society as a whole. It's not difficult at all to see how many "Jack"s nowadays are in key positions in the world, in economy, finance, politics, and so on... I'm from Italy and we currently have our own "Jack" prime minister ourselves.
I wonder if humanity will evolve someday to a point where we won't need/worship any such leaders anymore, if we'll become all "Piggy"s or "Ralph"s... or something completely different, in that one issue that the movie raises, even if less openly than others, is the purpose of human life - what for to be "Piggy" or "Ralph", what for to follow rules, if they mean you have to put your instincts and your nature away?
Sure in the movie they have a purpose - to go back home, and to that purpose Ralph's and Piggy's approach would've been the most effective and for sure Jack's influence was 100% detrimental, but in real life, what's the purpose? to which home we head to?
Metaphysical considerations apart, if you get home by following the rules, then we can think that in real life, following society's rules is a way to keep safety and "have your meat", and again to be safe and have meat in nowadays' world means to be safe from other human beings' violence and greed, so in the end maybe the circle closes - human nature IS evil, and our societies, our rules, are just a device through which we protect ourselves as a species from self distruction.