It's a textbook as much as it is a cookbook.
It teaches all the skills and information you need to be a good cook using "French Techniques". It's about 1200 pages. Starts with questions like "What is a cook", moves to kitchen sanitation, identifying and choosing ingredients, cultural differences in food around the world, and then starts teaching technique through recipes. Once you learn the proper techniques and means of choosing ingredients - you can basically cook whatever dish you want. It also teaches you preparation and organization.
Some people hop around trying out a few recipes here and there. Some people (like me) started at page 1 and follow it as sort of a curriculum. Without a professional over your shoulder you'll take longer and probably waste more food than normal - but it's probably the closest home-school method you can use. Afterall, it is the textbook of The Culinary Institute of America (CIA).
Even if you are an excellent cook already, it's great for recipes and reference. Hands down my favorite book in my kitchen.
Next on my list would be "On Food and Cooking" by Harold McGee. So long as you remember some of your high-school science, this book explains why food does what it does when it's handled/cooked. It's like the technical manual for all things food.