Chez Panisse Vegetables
Despite originating with an influential chef (Alice Waters) this is a great beginners cookbook. There is great info surrounding the veggies themselves and the recipes are simple and approachable. The only thing Alice forgets to mention, probably because it's seems implicit to her, is that these recipes don't really work with mediocre ingredients.
On Food and Cooking: The Science and Lore of the Kitchen
For the more technical minded, this book is nothing short of awesome. It covers the chemistry of cooking and weaves in a little history in the process.
The Professional Chef
This is a text book for the Culinary Institute of America, and while it reads as such (boring!) it is a great reference for everything that happens in the western kitchen. I seldom use the recipes, but I often refer to the techniques.
Mastering the Art of French Cooking
People often tell me they're beyond hope in the kitchen. Julia's Child started cooking when she was 32! This is her alternative to The Professional Chef, it's laid out differently, and includes a few more tricks. It's a great resource for people starting out and for people who have been at it for a while.
My Bread: The Revolutionary No-Knead Method
This book has a very specific skill set, but it has turned me into a bread baker, and anything that can do that deserves mentioning. It will have you making great bread at home without much trouble.
Chef Paul Prudhomme's Louisiana Kitchen
Ok, I realize this book isn't for everybody, but it's very close to my heart as it represents how I fell in love with food. This book is old-school, all of the recipes I've made have been great.