This is often called sideloading and the Nook might be best "ROOTED" to give you more options.
Googles for you:
Given a desktop PC with internet connection (60 mbps download speed) but no WIFI: Can content be added to an e-reader without using any WIFI?
The NOOK e-reader has a micro/USB port used by most for charging. Can content be downloaded from the PC (e-Reader store/website) to the NOOK using that USB port?