For those who don't haunt some of the book specific forums, you may have missed this one:
75% Off Two Books at Kobo
While they last, there are two coupon codes working
at Kobo for 75% off on any non-Agency book:
welcome75us and
welcome75ca. You can generally tell if the coupon code will work by looking at the price - if it doesn't end in .99 OR if there are two prices listed (for example: "List price: $28.99; Our price: $17.99"), then it is usually eligible for a coupon code.
To use the coupon codes, you click Buy Now, then search for the link that says "Have a gift card or promo code? Use it here" (if it isn't there, it isn't eligible for a coupon), click it, then enter the coupon code and click on Apply. I always double check the summary on the right, which will then show the promo discount and the total at the bottom, where what you will be charged is shown below the Buy Now button.
The coupon may be geographically restricted and these are the only two variations that work (US and CA). Each can be used one time and apparently were created for "new customers" to get a discount on their first books. However, it works for anyone (at least, it does for now, until they kill the codes).
I found quite a few interesting looking choices of eligible books, using searches for
Bundle,
Anne Holt,
Gluten-Free,
Annalise G. Roberts, etc.