Instructions:Just got this as an associated deal in a Boden e-mail, it states:
"Here's a page-turner of an offer for you; £5 off every £30 spent at Waterstones, plus free delivery. Just enter 'YF6842' at the checkout."
I don't know if that means that if you spend £60, you'll get £10 off, but as it's all free UK delivery now on (for who knows how long), maybe the code is useable more than once. Pretty good though, if you need £30 worth, it's about 17% off. Don't forget, 8% QuidCo as well :-)