The book should be a must read for everyone in a relationship. I had no clue what the 5 love languages were until my ex-girlfriend introduced me to the concept. It is VERY important for you to understand how your significant other perceives being loved.
Don't waste your time hoping you are speaking their love language. Sit down and take the fun little quiz and have a real conversation with them about how they prefer to be loved. Trust me fellas it will make your life that much easier.
Yessss you KNOW! :) It does make life earlier when we learn these concepts and make changes for the better.