Book Recommendation Engine/Affiliate Model

I just came upon What Should I Read Next, a search engine that allows you to put in the last book you read (or any book, I suppose) and get a list of recommended books to read next. For example, if you recently read Martin Amis' Money, you would get this list.

Of course, you can buy the books from Amazon, directly from that list. Take a look at the URL--it has the code "wsirn-20" in it, which connote that the site is an "associate", a part of Amazon's affiliate program.

Good for them. They've isolated a bit of functionality and used it to drive their own business.