This is a great book if you know how to use it. Its not for people looking for cookbook approaches. Rather, it provides well argued information about the underlying principles of visual design. The authors ilustrate their points about grids, layout, typography, and color by showing examples of top notch efforts by some of the best information designers in the world.
Classic examples like the London subway maps and the National Park Service brochures are illustrated, along with excellent explanations of the design principles that make these particular design so successful.
The aurthors then go on to show how these examples can be applied to GUI design. And they are very gutsy as they show actual examples from actual software products that are "design failures". In fairness, they also show examples of well designed software, with explanations of why the design works so well.
This book is for a person who's willing to invest some time to learn about things like information hierarchies and information design. Like playing a piano, this isn't something one can master over night, but also like playing a piano, it has its own vast rewards.