"The Non-Designer's Design Book: Design and Typographic Principles for the Visual Novice"

By Robin Williams (not that Robin Williams)

Quick, easy read geared towards non-designers (it's in the title!) that explains the basics of C.R.A.P. (Contrast, Repetition, Alignment, Proximity), 4 things that will change the way you look at things and stop centering everything :D

edit: formatting