First of all, you posted in completely the wrong section.
It says right on the purchase page that you need an iOS device.
The publishers want restrictions on what devices can read the books to make sure everyone pays.
In any case, if you ask google there are lots of converters such as Epubsoft Ebook Converter
I have never used it myself though.
Converters cannot convert any of the paid books, since those by demand of the book publishers carry copy protection and Apple has not provided a reader app for Android (or any other non-Apple platform). As Richard said, you can only view those books on an iOS device or a Mac running OS X 10.9. You cannot use them on Android device. If you want books that you can view on both your Mac and your Android device, you should purchase from Amazon, Barnes & Noble, or Google Books. They all provide reader apps for multiple platforms.