I transferred all mine to Sainsbury's.
They gave me a £5 voucher to get some more books.
I get a lot of old SF compendiums for about 50p each., so that was handy.
You can't download direct to the Nook though, now. You have to download to a Sainsbury's desktop app as a portable book format, then transfer to the Nook. Well that's what it said,. but when I did download them, it didn't require both these steps. My nook was connected to the PC, and the downloads went straight to the nook. Something like that.
I really enjoy it. I only paid £39 for a nook glowlight from Sainsburys in the first place.