I recommend Edward Tufte's books on information visualization (The Visual Display of Quantitative Information, Envisioning Information, and Visual Explanations). I'm surprised that I haven't seen these mentioned on LW before (except in passing once or twice). They're short but full of clear thinking about using graphic design to effectively communicate scientific reasoning. And even if you don't think you have much to learn from them, they're still beautiful books.

(I've heard his newest book, Beautiful Evidence, is not as good and mostly recycles material from the other three.)