There is no one correct way to approach a book like Animal Farm. In fact, it is best to approach all literature from various perspectives. In light of this, let me offer a few of the ways in which we can possibly read this novel.
First, a reader can look at the novel as an allegory of what was happening in Russia during the Revolution. Any introduction or preface will give you the basics. If we read it from this perspective, each animal represent someone or a group of people. For example, Snowball represents Trotsky, Napoloen Stalin, Box the working class, Mollie the aristocracy, and the list goes on. If we do read the book in this way, it is a clever allegory about Russian politics.
Second, even if we did not know anything about the Russian revolution (as most middle school students reading the book), we can still appreciate the themes of the book, the corruption of power, the power of rhetoric, the subtleties hypocrisy, and so much more.
In conclusion, it is best to read the book from as many perspectives as possible.