The Non-Designer’s Design Book, by Robin Williams. This is a great foundation book if you are new to visual communication and design. Williams addresses the four main principles of design—Contrast, Repetition, Alignment, and Proximity—in a very memorable acronym (CRAP). If you can master the four principles that Williams puts forth, you will automatically be a much better visual communicator. There are a lot of examples of how to improve bad design. This book is widely used in many intro to design courses in college.