Besides being a very well-designed book (as one would expect), this is a very practical and down to earth handbook for graphic designers. The emphasis throughout is on the techniques needed to convey a message, as opposed to simply satisfying a designer's desire to be different or to stand out.
This book is obviously useful for aspiring or professional graphic designers, but I think it would be useful as well for anyone putting together a website, writing a brochure, putting out a newsletter, etc.