THE classic book on nutrition has been out a long time --
Jane Brody's Nutrition Book. While it won't be up-to-date on some issues and buzzwords that have emerged recently, it is still good, solid, easy-to-read information. For example, she was warning about partially hydrogenated oils (what we now call trans fats) 30 years ago.
You can also get a lot of information from the web site for The American Dietetic Association (
www.eatright.org), and
www.nutrition.org.