Hi !
it’s normal, because by default, you (the camera) is also the spotlight. if a face is facing you, it gets a lot of light. if not, it get less.
it’s a rite of passage in sketchup, wondering why everything looks so dark 
in the shadow panel, if you click on the black/white button it will give you more options. The 2 options you need are the 2 dark / light sliders, they change the contrast of light and dark areas.
by playing with these (especially the dark slider in your case), you can lower the contrast of the shadowed areas, making your ceiling and pretty much everything in fact look less dark.
however, you’ll loose a bit of contrast, so you might want to add some ambiant occlusion to make the volumes more readable.
