Reading through comments, folks have used on box sets, Lego books, cook books, etc.

Take an extra 30% off any book offered by Amazon.com from now until December 1st. Enter code BOOKDEAL at checkout. Here's how [amazon.com](restrictions apply).

Terms & Conditions

▪ The promotion is valid for a limited time only, from November 27, 2013 at 9pm PST to December 1, 2013 at 11:59pm PST. Amazon reserves the right to modify or cancel this offer at any time.
▪ Offer only applies to products sold and shipped by Amazon.com.
▪ Limit one promotional code per customer and account.
▪ 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.
▪ The offer discount will be allocated to the highest priced book in your order.
▪ 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.
▪ Offer does not apply to Amazon Gift Cards.

Been able to apply code to my recent order via CS.