14TWAIN
Yesterday a 10% off code for the BookDepository was listed, but I was disappointed to discover that it only worked for a miniscule number of books. I found this code today and it worked perfectly.
You apply the code near the end of the checkout process. If you have a 28Degrees card, I recommend paying in Euros (you can switch currencies at the top right, but not during checkout). Doing the calculations, Euros worked out ~6% cheaper than $AU.
I used the conversion rates from here: https://www.mastercard.com/global/currencyconversion/
No ideas on what to buy? try this: https://wordery.com/the-halloween-oracle-stacey-demarco-9780…
Note: this code can only be used once. It might be possible to reuse it if you clear cookies for Wordery from your browser, use another browser, or create another account, but I haven't tested this.