From Slick Deals:
25% off any one book on Amazon is live again! (until Dec 14)

Terms & Conditions
To use this promotion, you must enter "25OFFBOOK" at checkout under the "Gift cards & promotional codes" section to receive 25% off any ONE (1) book, with a maximum discount of $10.
The discount will be applied to the highest priced book in your order.
This offer is valid on print books only. Excludes Kindle eBooks and Audible Audiobooks, Book Rentals and Amazon Gift Cards.
The promotion is valid for a limited time, on orders placed between December 10, 2015 at 12:00am EST and December 14, 2015 at 02:59am EST. Amazon reserves the right to modify or cancel this offer at any time.
Offer only applies to products sold and shipped by
Limit one promotional code per customer and account.
Each code may be used only once and may not be combined with other offers.
The maximum benefit you may receive from this offer is $10.
Offer good while supplies last.
Offer is non-transferable and may not be resold.
If any of the products or content related to this promotion are returned, the value of the offer will be subtracted from your return credit.
This promotion may not be combined with other offers, including promotional certificates.
Items must be purchased in a single order and shipped at the same speed to a single address.
If you violate any of the Terms & Conditions, the promotion will be invalid.
Void where prohibited.
Shipping charges may apply to discounted and free promotional items.