The Joann's store I go into I have no problems. You can use more than one coupon per order (not same item) if they have different codes on them (one from flyer, one from online or their bonus ones).....And the coupons take off the highest priced item at the register. Maybe the problem with the 40% coming off the book was because it didn't ring up at the sale price and the "computer" (don't we love em) calculated the higher priced item.
I shop JOann's often. Not for fabric as much as the cutting supplies. I usually use the coupons for the wide backing fabric though. The other closest fabric store is Hancocks and it is about 60 miles away. I have order some fabric online, but I like to see and feel what I am buying so that means I am limited to the local Joann's.