I agree, but I think it's worth noting that there's nothing inherently wrong with using referral links (if your review is honest and includes a disclaimer).
You could just add a disclaimer like: "I use Amazon Affiliate links to link to books I like."
I would use your disclaimer suggestion, but the few dollars that my Amazon link would generate is not worth offending HN readers. Getting feedback, creating discussions, and contributing to the community is more important here.
Thanks for the suggestion.