You really don't need their software to purchase the book, all you need Adobe Digital Edition. You can purchase it via the web and that's great. You need the Adobe software to download the book after purchase, I actually had a choice of which software to use (using a Firefox Browser) and chose the Sony Reader software to download the book.
I have screen shots and a brief tutorial for the Sony Reader Owners (Should also work for the Nook owners.)
http://sonyreaderboards.com/index.cg...lay&thread=626