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.