Another thing - if and when you do get around to buying a book in ePub, install Adobe Digital Editions first (free, from
here), and register your reader to it (by connecting it to your PC - the Adobe software detects it IIRC).
When you buy a book, you will then (sometimes) get a file which then opens with Adobe Digital Editions, which downloads the book and displays it. You can then copy the book, which will be in "My Digital Editions" within "Documents" on Windows, to your reader (using the Sony software, calibre or even explorer).