Modern C++ Design

Alexandrescu's Modern C++ design taught me how to template properly. Also, Scott Meyers's books were very helpful. The design of the D standard library has also been very influential on my code (Mainly convincing me of the benefits of ranges over iterator)

Armstrong's book on Erlang (2007) is a great read, so you're missing that. (Erlang itself I haven't really used much, but I like some of the concepts). Alexandrescu's Modern C++ Design (2001) is a real eye-opener (though I wouldn't use most of the stuff from the latter half of book in real production). Herb Sutter's books on Exception C++ (1999) are must-reads if you intend to use exceptions. at. all. [Whereupon, these books will convince you not to use exceptions in C++ :-) ]