Well, in the back of the book, there is a questionnaire so you can find your primary love language. I did it and as I tallied up my score I am fluent in not only one or two, but three different languages. (Yeah, I'm a complex woman.) Mine are words of affirmation (I regularly ask Jonathan why he loves me), quality time (I just like having him around all the time), and acts of service (I get so excited when Jonathan does something around the apartment without having to ask him to do it). Jonathan also filled out the questionnaire and it was so enlightening to see what makes him feel really loved.
I think this book does a really good job of simplifying the various aspects of love and helping couples be more aware of what their spouse needs to feel loved. I haven't read the entire book, but I feel like it has already made me more aware of Jonathan's feelings as well as my own. Here's a website that goes along with the book. You should check it out.