Amazon recommends either really well or really poorly

So today I had a new experience with Amazon.com: I'm waiting on a book that was supposed to arrive about the middle of last week. This morning I checked, and the book was loaded on the UPS truck, headed my way.

I'm sitting in the office today, and I get an "Amazon recommends..." e-mail. Something about the book seems familiar, so I click through, and it's the book I'm waiting for Amazon to deliver!

It seems to me that the sophisticated recommendation algorithm might skip those books that it has reason to believe you already own ...