Stephanie Alexander's "Cooks Companion"
This is easily my favourite cook book of all time. Stephanie Alexander's "The Cook's Companion" is as much a resource to learn about about food, as it is a recipe book. It is particularly good for Australian cooks, as it is specific to our seasons and produce. It is not an encyclopedia of food, but it is an amazing collection of vital information for anyone serious about cooking great dishes.
The book is organised in order of indredients. For example, if you wanted to cook a lamb dish, go to the lamb section and Stephanie talks about seasons, cuts of meat, ways to cook different cuts, foods and flavours that complement the ingredient etc.
There is also the 'Basics' section where she gives direction to create all the basic techniques you need to start most dishes, like stock, pastry, Beurre Blanc, Mayonnaise etc...