I've just finished reading through "Universal Principles of Design" by William Lidwell, Kritina Holden, and Jill Butler. Overall, it is an excellent book containing about 210 design aspects (80/20 Rule, Color, Consistency, Alignment, Readability, Rule of Thirds, Symmetry, etc). Each design aspect fits on a page and is accompanied by graphics to illustrate.
This is a good read that will allow the reader to make better decisions in design and which will require thought to be put into the decisions. After reading this book, the reader should understand the importance of displaying clear messages and error codes, simplicity is sometimes preferred, readability and legibility are required, how to determine beauty in faces and the human form if using a model, and how to use the Rule of Thirds in the design composition. All usability experts should read this book and have it on their book shelf.