A:
Yes, it is possible. Without WiFi, it is more difficult but very doable. Simply sign onto your BN.COM account and in the upper right corner you will see "My Account." A drop-down menu appears and you'll want to click "My NOOK Library." Your library will appear and next to each book will be a large "download" button. Click that button and download the books you want to add to your device - this will download the raw DRM protected ePub file for your book(s).
At this point, make sure you plug your NOOK into your computer if you haven't already. Follow the instructions in the user guide to sideload the ePub files you just downloaded onto your device. Once the files are loaded, follow the user guide instructions to safely remove the device and from that point you will be able to begin reading.