Something I wrote about those a few days ago:

http://news.ycombinator.com/item?id=4360330

I took the time to recommend some books that were very specific to the thread at hand, that I had taken the time to read and evaluate. Getting a few extra dollars to buy more books with, that costs those clicking nothing, seems like a mutually beneficial transaction in that it makes me more likely to read some interesting books I can recommend in the future.

So: yes, they were. If you don't like them, don't click on them. If you think my account is a spam account, created for the purpose of spamming HN with affiliate links, feel free to report it to Paul Graham.