Animal Farm, George Orwell
Well, . . . yes.
The thing about Animal Farm is that it’s so simple a child can read it, and – better yet – understand it. And yet, it’s absolutely an “adult” book.
I can’t think of any other story that so clearly shows the decay and bastardization of a good idea. You see it coming, you know it’s going to go bad, and yet it still surprises you. No other book has made me actually want to call out and warn the characters of what’s happening, and the fact that you can’t do anything to stop it is what stays with you long after you put it down.
Animal Farm may have been written to depict the Russian revolution and subsequent installation of communism, but it just as easily applies to any and all governments today, regardless of ideology. All books about human nature are equal, but this one is more equal than others.
(also: Lord of the Flies)