This is a collection of the original books, translated by Srila Prabhupada and published from 1970 and later. If you want the edited and improved versions then visit & register at bbtmedia.com. There you can download the latest book in various formats for Kindle, Sony, iOS and others. Registration is required.
Does your eBook reader not support epub ?
The Amazon Kindle does not support ePub files. If your device is also stubborn and refuses to open ePub files then you can convert ePubs (and other formats) on this website. To organize your collection of e-reader books there is a free program available called Calibre. Download here.