I read this book, back when I thought I was in R (turned out to be false R). I thought it was a great book, but it did show me what was lacking in my marriage.
I think it also helped clarify, for me, what a great marriage/relationship is supposed to be like, and I've used what I learned from the book in my relationship with my SO.
Just remember, both people need to be willing to work together to build a really good relationship. If you're both not on the same page, it doesn't matter what any book says.