Looking for a good book on the principles of graphic design? Here are my suggestions…

Graphic Design The New Basics (Ellen Lupton, LOVE her.)

Greg Berryman (Basic, of course, but still pretty good!)

Universal Principles of Design (This is not specific to graphics but covers a very broad range of principles simply)

Digital Foundations Intro to Media Design (This was the text book I had to use when I taught at CSUF, it covers everything from the perspective graphic design with computers.)

I would suggest heading out to a bookstore and trying to look at these books yourself before deciding, but this should give you a starting point.