Mine is a well-worn copy of The Joy of Cooking. Although I don't make a lot of actual recipes from it, it's my go-to for reference.
I suppose if I were a little younger, I might use Bitman's book for that, but when I was learning to cook, Bitman wasn't writing! Old habits die hard, so I still grab Joy when I'm looking for informtion.
Interestingly, my mother used BH&G as her first source, and I find that I still use it frequently (but not as much as Joy).