How do you get Amazon so you can: find a book they are selling advertise it for them by putting a link to it on your site make money when someone clicks on the link without having to own the books or pay them anything?
You can join the Amazon affiliate program at associates.amazon.com - you can add links to individual books, or use their contextual thing, but it's not very accurate. Amazon doesn't seem to convert very well though - most people who want to buy a book go straight there these days, so you don't get much except for people seeing a review then maybe clicking the link.