Um ..... Am I the only one that is totally lost?
Who cares if it is a different operating system or not? (although Harry is correct, it isn't) What does that have to do with Amazon being a Monopoly (which they aren't)?
And what other answer could there possibly be then to buy a different product which suits your needs?
From the structure of your posts, I get the feeling that English is not your main language. I suspect you'd be better off with an ePub reader which would allow you to more easily purchase from other sources than Amazon.