My take on the Gang of Four book is that it said more about the role of interfaces than almost any other book on object-oriented design.

Madame Mao’s ‘Gang of Four’ saw it as the most dangerous of all Western instruments.

This is one of the more famous books among professional programmers, and has become known as "the Gang of Four (GOF) book," based on the collective nickname of the authors.

We have criticized, on both a theoretical and a practical level, the phoney, ultra-Left socialism pushed by the Gang of Four, which boils down to universal poverty.

His Webpage, along with downloads of code implementing the Gang of Four patterns is at http://www.cs.ubc.ca/~jan/AODPs/.