<p>I have been a developer for 10+ years and so far my IIS knowledge is just enough for deploying stuff on it and get it running. Recently I have been playing with IIS 6 and realize the huge difference on the worker process model. I think I would need some good guide to update my knowledge in this area. Any good article/book recommendation?</p>

There are several online resources, starting with this one:
Performance Tuning (IIS 6.0)