If I refer someone from my website to buy a book at amazon, but instead of buying that book the visitor will buy another book/s or will buy the book I used to refer with plus other books. Will I get the comission on all books? or only on books that I have used to refer with?
If your affiliate id is linked to the url that the customer makes a purchase thru then you will be credited for the sale. Its all about having your affiliate id linked to the sale!
Depending on how you link it, the first book, if they bought is, is a direct link sale and any others would be indirect link sales (so different commission %).