Yes, this book can be very useful for couples...
It can be very eye opening and informative for young couples (relationship wise) who thought they knew each other...
Without such a book, many people would tend to mistakenly assume that their partner would logically feel loved via the same types of things that make them feel loved... They would be gravely mistaken...
To know your 'love language' is one thing; but they only way for this book/tool to be useful is if each member of the relationship is willing to learn what their partners 'love language' is - and go above and beyond out of your way to show them such love - always...
while words of affirmation and physical touch are mine - it is important that couples do not demand to receive such love from their partner nor swibble over 'you don't love me bc you don't abc'...
Rather (just like christmas) it is more important to give than to complain about what you didn't receive...