The book’s arranged according to subject, and analyses the development of the sign as language. The text’s in German, French, and English, featuring work by Paul Rand, Adrian Frutiger, Lance Wyman, and many other renowned designers. It’s essentially a vintage edition of Hyland & Bateman’s Symbol.
Thanks for the tip, Stephen.
You can see a Flickr set of another Diethelm book, Visual Transformation. Not logo-specific, still interesting.