Keeping a small room visible all the way to every wall is the goal. Dark corners or walls make a room seem to shrink in size, and a dark ceiling shrinks headroom.
Layering light in a room resolves the problem: Spread the wattage around by using several lamps around a room, and in rooms with overhead lighting, banish the ubiquitous center light in favor of several smaller lights. (That doesn't mean you have to give up having a ceiling light; just reduce its wattage and give it some company.)
Vary the height of the lamps, too, to ensure that the room is lit top to bottom. Small lights tucked into bookshelves add a soft glow to dark walls at near-ceiling height. Floor lamps can be used not only to illuminate the page of a book you're reading but to cast a gentle circle of light on the floor.
