Kobo have several very generous coupons right now:
Welcome75us – 75% OFF expires today
Welcome75ca- expires today
AND Welcome90us- 90 (!) %OFF expires… sometime.
Welcome10us- 10 dollar discount ( The book has to cost at least 10 dollar for it to work)
Welcome5us – 5 dollar discount
Welcome50us- 50 percent off (!).
I have used them all, and saved lots. At least 50 dollar. Edit: I counted, and I have bought 80 dollars worth of books, and paid less than 30 dollar for them. (I aimed for the 15 dollar plus e-books for the big discounts, and used 10 dollar off on books that cost 11 dollar. )
Johanna Lindsey’s backlist is on sale for 3.99.
For paper readers, The Bookdepository offers an additional 10% off. Add APMA12 during checkout.