Almost every graphic designer knows Designing Programmes by Karl Gerstner. The book, from 1964, had a huge impact on my (Martin’s) systematic approach to design. In an interview conducted by Ulrike Felsing, Gerstner declared logos unnecessary. Gerstner developed systems, or programmes as he called them, that would be recognisable by themselves.
Semiology of Graphics: Diagrams, Networks, Maps by Jacques Bertin was a real eye-opener for me back when I wrote my doctoral thesis about flexible visual systems in communication design. Although Bertin was a cartographer and Semiology of Graphics is a book about the theory of information design, it shows how to build flexible visual systems with graphics like no other book I have read.