If you're looking for a great intoduction to photography book that you'll want to hold on to, this is the one. Not only is it filled with everything from a discussion on exposure to all the formulas you'll need to calculate magnification when shooting macro, but its also filled with amazing photographs. Shaw presents the fundamentals to beginners in a concise but clear manner, with great diagrams and schematics. DoctorIt started with this book, and he recommends it to you as well!

Not a very expensive book either, check it out at Amazon: John Shaw's Nature Photography Field Guide