I think it's general Internet etiquette that when you are referring a community of people (that you are a member of) to a specific product though your own site,

I think it's general Internet etiquette that when you are referring a community of people (that you are a member of) to a specific product though your own site, you don't pass in a referral code. It shows that the product you are talking about is actually recommended, rather than a quick money maker for yourself. I don't have a problem with the website in general, especially if I found it through Google. But, what's to say that 10 other HN'ers don't post a book review tomorrow with an affiliate link? Because, after all, it's profitable. Who cares if the book is good or not? Given the OP's unofficial librarian status, I don't think it's a major offense in this case. But, I didn't find that out until after I posted my first comment.