If you want to read Sony books on a Sony ereader, then follow the link in my other post.
If you want to read Sony books on your Nook, then you skip the step in the Sony website explanation to authorize your ereader with the Sony Reader Store. You just want to register your computer only with the Sony Store. You want to download Adobe Digital Editions software and authorize your Nook with that. You want to make sure that the Sony Store and the Adobe Digital Editions software are both linked to the same Adobe Account ID. Here is a link to a page which explains the process step-by-step. It is a little outdated. The Sony Store now downloads your EPUB files into a folder called \Documents\My Books\Reader Library.
http://ireaderreview.com/2009/12/13/...ebook-support/
Here is a link to a similar thread in the Nook forum that you might want to jump to if you are a Nook user.
https://www.mobileread.com/forums/sho...d.php?t=108200