Benjamin Nevarez (blog) has been working really hard on a book on the Query Optimizer. It just got finished in time so that there will be copies available at the PASS Summit. I strongly recommend you track it down. There’s a lot to learn between the covers. How do I know since the book just got finished and isn’t in anyone’s hands yet? Because I’ve been watching it get built. I put in my small efforts as the technical editor. I feel bad about that because I’ve always learned from my technical editors and I’m fairly sure I learned more from Benjamin than he did from me. Get a copy of the book. You won’t be disappointed.