How to Cook Everything by Mark Bittman was the first cookbook I bought. I used a gift certificate I got for college graduation, went to Barnes and Noble, and picked it up. My copy is thus over 10 years old, so it doesn't have any of the stickers denoting the many awards it's won since its initial publication. I'm quite proud of the fact that I "discovered" it, and it has shaped my cooking immeasurably. You can see by the open book picture that I use it often, and I can't bring myself to buy a new one! There are still many many recipes I haven't made and many sections I haven't read yet--the long narrative introductions to each type of food are great and have expanded my food knowledge. Other great features: suggested menus for various occasions, an amazingly detailed index, and, for many recipes, a list of suggested alterations (like 8 different skillet pork chop recipes).
The bright green book, How to Cook Everything Vegetarian, is just as massive (They each have over 900 pages!). I received this one for Christmas, and I'm excitedly working through it. I would not have thought it possible to do a vegetarian book on this scale, but he covers all types of beans, rice, various grains, tofu and other soy products, and of course vegetables.
So, if you like lots of text, or playing around with a basic recipe, or just want to learn, I'd highly recommend these books. If you can only cook with pictures and want just one recipe per page, I'd recommend his The minimalist cooks at home, currently available in Anastasia's Picks at the public library.