Here’s an awesome Amazon deal for you! Right now there is a Buy One, Get One 50% Off Promo on Select Books, plus I found some titles on sale up to 60% off regular prices already. When you buy two books, you can save up to 70% off original prices with the stack. Here’s the link to check out everything that’s available:
BOGO 50% OFF Books Promo at Amazon (Stacks w/Sales; SAVE UP TO 70%)