Are you familiar with the theory that Number was Heinlein writing a how-to manual for writers of adventure fiction? The "black hat" villain figures that drive the action all have names that are anagrams of Heinlein's (or his wife's). The ongoing argument over what world they should raise the kids on highlights that settings that are comfortable to live in aren't the ones conducive to adventure fiction. Discussions of poor writing occur in the foreground of the book, with examples of proper technique going on in the background.