The color-book style guide: line weight, whitespace, and page balance

Great coloring books share three properties: clean bold outlines, generous whitespace, and single-subject pages.

Line weight should be 3-6 pt at trim size. Thinner lines disappear after printing; thicker lines feel childish. Bookart Studio's illustration model is tuned for this range by default.

Whitespace matters more than density. A page with one big lion and a lot of empty background is more fun to color than a page with six small animals — kids get overwhelmed by clutter and give up.

Rotate composition across the book: full-bleed page, centered vignette, portrait subject, landscape scene. Variety keeps the flip-through interesting on Amazon's Look Inside preview.