I think it would be better to write a book on creating a specific type of game with Blitz3D. I feel that it would be pretty easy for me to write an entire book on how to create something like True-Vol. That game pretty much used all of Blitz's capabilities at one point in it's development or another. I wouldn't mind writing a book on something more focused like that. Creating 3D games in general with Blitz I think would be too wide a focus.