I just received a Nook HD and ADE isn't picking it up under Bookshelves. I have been using ADE with my first addition Nook for 2 years now successfully. My Nook HD is set up with Barnes and Noble and I have already bought a few books. I connected my Nook HD to the computer (it is turned on) then opened ADE. I downloaded a book from my library that ADE has listed in my library.
How do I get ADE to recognize my new Nook HD?
See the thread http://forums.adobe.com/message/4915743 for lots of info on Nook HD.
Post 6 has one answer to your question; and you will find other useful comments on the thread as well.
It's quite long, so I'm not copying it here.
If you install the Overdrive app on the Nook you can download and read library books directly without using PC or ADE at all.