Some have suggested that rooting and eliminating some processes will stop the practice, but the only way I could see that working is if you turn off library sync entirely. I don't think that BN are sending the books to the nook directly, they're being added to the ebook libraries associated with our accounts and then synced to the device when we sync the library. It is possible to "archive" these books from the nook itself, so at least we can get rid of them, I'd prefer if BN just didn't do it in the first place, though. I didn't pay less for my nook, why is it suddenly behaving as if ad-supported?
"dread and fear should not be confused; by dread I'm inspired, by fear I'm amused."