I would recommend the book Ruhlman's Twenty (http://www.amazon.com/Ruhlmans-Twenty-Techniques-Recipes-Manifesto/dp/0811876438). It's not a cookbook, though it has recipes -- it's a thorough overview on the purpose of twenty basic ingredients in cooking (water, eggs, butter, salt, etc.).

My primary resource was The Four Hour Chef by Tim Ferriss. It isn't a recipe book (though it does contain recipes), but rather is a book describing how to actually cook, like how to do various techniques of cutting and braising, and what tastes go together, and how to learn what tastes go together.

I recommend it, but this isn't the kind of high-quality recommendation you get from someone who's tried a bunch of things and has an informed decision about which one is the best.

As I was working through the book, I asked a much more skilled-at-cooking friend for recommendations, and she said that On Food and Cooking by Harold McGee is highly regarded. I haven't checked it out yet.