Cash Baq, you earn $4 cash back for each book = $8 back or $4 for both books ! PLUS if you are new to Cash Baq, they will give you $5 in your account! It makes this a $1 money maker!
The coupons don't expire until November 2010. You can grab your deal HERE.
You could also go through Shop at Home HERE and get $4, BUT I think they are just giving you $4 for buying both books.