How THE book relates to Stalin and Hitler

Well, Obviously Big Brother is the same kind of potentate as Stalin and Hitler. I suspect that Orwell had his eye on Stalin rather than Hitler. Big Brother even looks like him. Furthermore you could argue in both directions, since most totalitarian states are rather similar. Big Brother has focussed hatred on his enemy Goldstein (Trotsky / jews), he is head of "the party," he has a powerful system of censorship, propaganda and torture. Then there is the fact that the individual needs to conform to the party and history is rewritten to suit the ideas of the party.