Dennis M. Ritchie passed away yesterday. He was a pioneer of modern computing; one of the fathers of Unix and the developer of the C programming language. From these two foundations has grown most of the software tools and technologies that we all depend on every single day.
He also co-wrote "The C Programming Language". The book, like the language itself, is masterful in its brevity and clarity. It aims to describe the language, but managed to teach me an enormous amount about programming in general along the way, and in fewer pages than the introductory chapters of some programming books. It is one of my all-time favourite books and I still leaf through it from time to time.