Add a strategy guide to your cart and enter "BOOKDEAL" at the checkout under "Gift cards & promotional codes" section to receive 30% off OR $10 MAX off. Limit 1 per account.
I personally just tested this on a few guides at random and ended up pre-ordering Lightning Returns with it. Once it's locked in, I've never seen a promotion be taken off (if the price changes the discount will however update) unless you cancel so you can order with confidence. Sorry in advance if this doesn't work on all guides because obviously I can't test them all. :P