on 07-16-2012 01:46 AM
For books you bought from B&N:
If you have an N1E, connect your nook to your PC via a USB cable, and copy away. For all other nooks, you cannot, unless you root. The workaround for this is to install the Nook for PC application on your computer and to download from there.
For books that you sideloaded:
Connect your nook to your PC, go to the folder that you transferred the books into, and copy them back to your PC.
I keep two folders - "Books from B&N" and "Non-B&N Books" (those in the second group are either Adobe Adept DRM or no DRM books) and I backup both folders to my cloud share, so my books are on my nook, my PC, and my cloud storage.