Since Pat Hanrahan was part of the reason for starting this project, it was only fair to ask him first. I also didn't get all the titles written down that he mentioned, so there is also a practical reason ...

Pat Hanrahan is a professor of computer science at Stanford, and has published not just in visualization, but also in many other areas of computer graphics. Instead of listing his achievements here, let me just tell you this: if you don't know who he is, you better find out.

Here is Pat's list, including his comments. I only added a few authors' first names and links to Amazon.com (for convenience, no endorsement, affiliation, or anything).

• The Elements of Typographic Style, Robert Bringhurst
• The Camera, Ansel Adams
• Perspective and other Drawing Systems, Fred Dubery and John Willats
• The Semiology of Graphics, Jacques Bertin (tough, but worth reading multiple times)
• Art and Illusion, Ernst Gombrich (good antidote to naive realism)
• The Psychology of Art, Rudolf Arnheim (alternatively, Visual Thinking)
• The Optics of Painting, Hermann Helmholtz (classic essay, good introduction to tone mapping!)
• Eye, Brain and Vision, David Hubel
• Eye and Brain, Richard L. Gregory (alternatively, The Intelligent Eye)
• Instruments and the Imagination, Thomas L. Hankins and Robert J. Silverman (good introduction to history of graphic devices)
• The Science of Art, Martin Kemp
• Picturing Time, Marta Braun (biography of E. Marey)
• The Senses Considered as a Perceptual System, James J. Gibson (alternatively, The Ecological Approach to Visual Perception)
• Things that Make Us Smart, Donald Norman (most of it has to do with visualization!)
• Inner Vision, Semir Zeki (artists as neuroscientists?)