Personally, this has probably been the most influental design book that I own. I felt like I was a better designer after having read half of it, without once touching my mac. i just knew that what I had absorbed was going to come out in my work, and it did. The book takes an overview look at design, and speaks in plain english about many things that I've heard or dealt with. But catagorizes stuff and explains things in a fluid manner so that the different bits of information come together and make sense. It is good for the novice and the struggling self taught. Full of great examples. It's too elementary for the serious designer. But for someone who did not go to Design School, but now works with design, its the perfect basic "education in a book".
This book and some of the other books from the Design Briefs series, have become an integral part of my working resource library. Ellen Lupton's book has been one that I have used over and over again. I often reference it when I am faced with a blank page that I am having a hard time laying out.
The section on typography, the largest section of the book, was a very interesting read. I enjoyed learning about the history of printing and typography. Beginning designers will appreciate the categorizing of typefaces. This leads into the discussion of electronic typesetting and the limitations and challenges that has created for designers.