If you're familiar with this book, you might think, "Hasn't everyone heard about this book or at least the concepts presented in it?" I'm sometimes surprised by people who haven't heard of it. Personally I think the concepts Gary Chapman identifies and describes in his book are revolutionary in relating to anyone.
He identifies five primary love languages that each person has - some may have more than one that is primary and everyone has some that are secondary. Your love language is the way you feel loved by someone else, and often the way you show love to others. The languages are: Words of Affirmation, Quality Time, Receiving Gifts, Acts of Service, and Physical Touch. Perhaps you can identify yours from this simple list. The book goes into great detail and examples of how people with each love language feel loved and give love. If you can identify this about yourself and your spouse; or about anyone in your family or circle of friends, it will help you understand and appreciate your differences with them, and therefore relate to them better.
My only criticism of his book is that I think he left out a 6th love language - tasty food. I feel very loved when my husband takes me to a yummy restaurant or cooks me a delicious meal. I feel loved when someone invites us to their home for a meal, or delivers a tasty treat. I love my family by creating pleasing dishes for them to enjoy. I love myself by ordering Papa John's pizza, or getting a mint chocolate chip hot fudge sundae, or by eating a Reese's peanut butter cup. Food definitely speaks love to me. And, just for the record, I am not overweight because of it.
If you'd like to specifically apply these love languages to other relationships besides your marriage, and want extra details and examples, you can check out Gary Chapman's other Love Languages books. "The Five Love Languages of Children", "The Five Love Languages of Teenagers", "The Love Languages of God", "The Five Love Languages: Men's Edition", and "The Five Love Languages of Singles". His website is http://www.garychapman.org/