Here's an outline of what the book will include:
Part 1: Chapters about Philip Pullman, the influences on him, etc., and chapters about the three volumes of His Dark Materials.
Part 2: Chapters about the big philosophical and theological themes which Pullman explores.
Since it's a 'thinking fan's guide' it will be both enthusiastic about the trilogy and subject it to some probing criticism in Part 2. I was fortunate to interview Philip Pullman in late 2002 and I think he enjoyed a little intellectual sparring as much as I did. The interview may go in as an appendix. I hope to have enough time to write an appendix on the science of HDM.
I ought to stop for now - my editor is expecting a chapter from me tomorrow and I'm nowhere near finishing it yet!