Resources

If you are you are just starting out then you need to start at the beginning. There is no better resource to get you up to speed quick then AnswerMan Principles of Air Conditioning. This manual is small in size but very large on information. It is easy to understand and follow making it the best place to start.
If you are the type of do-it-yourselfer that prefers to study everything you can before digging in, or you just desire a quality reference book then Modern Refrigeration and Air Conditioning is for you. This book is detailed and in depth.