If you're selling books, I don't know if there is a difference between B&N and Amazon. But you will always be pleasantly surprised by the visitors you send to Amazon, they think it's an on-line shopping mall or something!
I market mostly their non-books stuff. Conversion for me is usually at least 3%, and my EPC is over $3. Just upped my traffic on the last Google update, and today's stats will help me sleep well tonight...except I always get more ideas when I'm trying to fall asleep.
I use a script called amazon.pl from Cusimano.com for a lot of pages. I can then make keywords linked to amazon search results, or pull results into a nice little box by a SCRIPT tag, or a bunch of other uses.
2 sales in 2 years with 1418 click throughs and lot's of creative changes to try and stire up sales. Dead BF dog but I refuse to jump on Bezos's bandwagon when Amazon stiffed me on some consulting fees and bringing them Toys-r-US and Overstock SKU's. Who wants to promote an easy URL like Amazon.com seen at 2 million web sites??? These all are impulse buys and the 3 Amazon storefronts I set up for clients do squatt in sales after they stopped the cross linking off book keywords.