ThriftBooks does 15% off for educators, but you have to verify through SheerID first to get the promo tied to your account. Heads up: it only kicks in on used items, not new copies. It stacks with ReadingRewards points, though. Just make sure your cart hits $15 so you don't lose it to shipping.

Just use a throwaway email to grab that 15% welcome code if you've ordered before. Just make sure your subtotal stays over $15 *after* the discount hits, or they’ll tack on shipping fees. Definitely join ReadingRewards at checkout too; points stack fast and earn you a free credit every 500 points.

Skip looking for promo codes online, they almost never work. Just use their ReadingRewards program instead; points add up fast for free $5 books. Definitely bundle your orders to clear the $15 free shipping minimum, and keep titles on your Wishlist so you get alerted when cheap copies pop up. Watch out for ex-library tags though.

Honestly, once you hit submit on ThriftBooks, it’s basically locked in. Their automated warehouse system grabs it immediately. Customer service can’t even intercept it 99% of the time, even if you message them within five minutes. You'll just have to wait, start a return in your account dashboard, and eat the return shipping.