This is an important book, because it makes two important points through an allegory. Let me unpack this sentence.
The first important point is that it shows the nature of people. The book shows that absolute power corrupts people. At first the revolution starts off as a good idea, even noble, to set the animals free. However, as the story progresses, the pigs are even worse than Mr. Jones. Often this is what happens in our world. There are great promises of freedom and what ensues is a different kind of slavery.
If we look at the book as a historical allegory, then we can see the book as a political commentary of what is happening in Russia. The parallels between Napoleon and Stalin, and Snowball and Trotsky, are clear. Eventually, Stalin exiles Trotsky, as Napoleon drove out Snowball. The point is: Is Russia any better? The answer is no.
Finally, because the novel is an allegory, it has a way of making us think of the dynamics of power in a non-threatening way. This allows us to be critical. When we have done this and apply it to our world, then there might be a new way of thinking.