Don't let the clip art and lack of color put you off this book. In fact, the extensive use of clip art make this a fun fast read. Horn gives us a compilation: basic concepts; history; research and reference; and the some how to's in using visual language. Just don't expect to see the current state of technology and design for creating visuals and infographics.
As a practitioner of visual thinking, I'm glad to have this on my shelf.