Food Rules is essentially a compact and condensed version of Pollan's other works. Some will be familiar to anyone who has read his books, such as "Don't eat anything your great-grandmother wouldn't recognize as food." Others were simply great reminders, such as "It's not food if it is called the same thing in every language (think Big Mac, Cheetos or Pringles)", "Don't eat cereal that changes the color of your milk" and "Drink your spinach water" (he advocates using the water we cook our veggies in, which is in itself full of rich vitamins and antioxidants, by adding it to things like soups and stocks).
Overall, Food Rules contains nothing new to conscientious eaters but it does provide some great reminders in a compact book that will help you live a healthier life and make better food choices.
You can read a Q&A with Michael Pollan about this book from the New York Times here.