I'm really torn regarding the formatting for Walkabout.
I've already decided that I'd like the rules to be generally separate from the majority of the setting material. There will be bleed between the two. For players, the character creation section in particular needs links to the setting. For GMs, the rules for creating story will need to link to the setting from a meta-perspective.
I'm finding that there is a bit more creep of setting into the rules than I had initially anticipated, especially once I start including play examples...and the book is starting to bloat.
I know I've been down this road before, but I'm starting to wonder again whether I follow the path of separate Player's guide and GM's guide.
That means a minimum of 3 books. One for setting, one for players (including basic character generation, task resolution, story framework and character development), and one for GMs (including details on spirits, developing stories and settings, and how to get the most out of the mechanisms within the game).
With a seperate setting book of 80 pages or so, the all-in-one core book is currently looking at 160 pages. Splitting it might make 3 80 page books (a good split for a boxed set).