Assume that all of these are available to all customers unless specifically listed as member only like the Welcome Package. Also remember that any preliminary codes are just that and BN could pull it, change the details or exclusions anything prior to release so always a bit of YMMV until the final release date

Mini FAQ
Coupons should not work for PREORDERS , Nook, Legos, Rosetta Stone, Digital, Gift Cards, Memberships, etc. There are glitches where sometimes an excluded item will be allowed but assume that is the exception to the rule
Free Shipping is $25 (before tax/shipping) or with membership.
Max 3 GC on a single online order.
Online only a single code can be applied to an order
Return period is 14 days after delivery (possibly 30 days for members though I've never tried)
Online ordered items can returned to a local store unless it's classified as a web-only item then it's at the store's discretion to accept
The long standing Free 60 day Trial Offer was discontinued in late May 2016


STORE ONLY 15% OFF Coupons -- Unknown if multi-use or if will work on 40% Off Items
15% OFF Single Item Exp 12/31/2017 (I)
15% OFF Single Item Exp 12/31/2017 (II)
15% OFF Single Item Exp ?? (III)

20% Off Single Item Online
D4M8K3B -- Unknown Expiration. Could be 11/24 or it could be Dec 31 exp

Store Only Coupon
25% Off One Item
coupon is valid at Barnes & Noble stores from November 24, 2017 to November 26, 2017 at close of business.

ONLINE ONLY
GIVETHANKS
valid 11/23 through 11/26 -- I'm guessing ending 11:59pm PT though it's possible they'll stop it ET and start a Cybermonday code


DAYMAKER 20% off $50 or more
Expires November 22, 2017 at 11:59pm Eastern Time.




Some possible upcoming codes
TAKEFIVE

"New Member" Welcome Coupons
Welcome coupons may be dead -- or at least the type that have been available for nearly a decade. The latest set now have what appears to be single use codes so these probably no longer will be generic/multiple use style.